General ZvT Strategy
 Unit Roles and Counters
- Zergling: In numbers, decent against all ground units if they can get a surround. Metabolic Boost helps against ranged attack. Siege Tanks in siege mode kill a Zergling in one hit unless the Zerg has at least one Carapace upgrade and the Terran has no vehicle weapon upgrades.
- Roach: Strong against Hellions, moderately effective against Marines, countered by Marauders. Burrow and Tunneling Claws can improve effectiveness, but are rendered nearly useless by Scanner Sweeps.
- Baneling: Very strong against Marines, but less so against Marauders. Useful to destroy Supply Depots in Terran wall-ins.
- Hydralisk: Strong unit, but fragility and slow speed makes them very vulnerable to the entire Terran arsenal.
- Mutalisk: Very useful for harass and against unsupported Siege Tanks and Marauders. Use Mutalisks' superior speed to avoid groups of Marines. As a light unit, Mutalisks perform well against Vikings. Be sure to use proper micro against Thors to avoid their significant splash. ()
- Infestor: Powerful unit but, as a pure spell-caster, it requires good control. Fungal Growth is extremely effective against Terran bio-balls. Neural Parasite is handy against mech-heavy compositions.
- Corruptor: Strong against rarely seen Battlecruisers, less so against Vikings. Usually seen only just before they are morphed into Brood Lords, but are a crucial element of the increasingly popular Infestor/Corruptor/Brood Lord composition.
- Brood Lord: Very strong against ground units, but fall to Vikings. They are extremely effective against Tank-heavy compositions because the melee attack of Broodlings causes friendly fire.
- Ultralisk: Splash damage very strong against Terran bio-balls, particularly in combination with Fungal Growth. Upgrades are key.
 Drone Scout
Barring some kind of fast pool build, you should always scout the Terran base early in the game with a Drone (usually around 13-14 supply). By doing this you can get some important information:
- You can see if Terran is going for a 2 rax build, a 1 Rax FE, or a Rax-Refinery build, all of which should be responded to differently.
- In addition, if you see nothing in the Terran base, you know that there are proxy Barracks somewhere, and can immediately begin preparing for a rush.
- If you see that Terran went for a Rax-Refinery opening, you can steal his second gas geyser to prevent him from doing any gas-heavy builds.
 Early-Game Scouting
Since Terran will always wall their ramp it can sometimes be difficult to scout exactly what Terran is doing. However, by using a combination of different scouting techniques, knowing common Terran TvZ builds, and using some educated guessing, you can usually be prepared for most builds.
- Scouting the ramp - if you are unsure what Terran is doing, you should constantly scout your opponent's ramp by sending a Zergling up the ramp. If Terran has any units at your opponent's ramp, you will be able to see them and respond accordingly
- Knowing common openings - if your initial Drone scout sees 2 Barracks, you can being preparing for a 2 rax. If your Drone scout sees a Rax-Refinery build, you can expect a Hellion expand build, or Hellions followed up with a Banshee Opening.
- Sacrificing an Overlord - this tactic is one of the most important ways Zerg has of scouting Terran. After Terran walls off their ramp, they can go for a non-standard build or an all-in, and you cannot see inside your opponent's base to know what your opponent is doing. By flying an Overlord in, you have a chance of seeing the buildings inside the Terran base, thereby seeing what build your opponent is doing. However, since Overlords are very slow, it is possible your Overlord may not see anything before being shot down by Marines. The best time to send in an Overlord is between 5:30 - 6:00 game time, since Terran will have already committed to a build. You must prepare for sacrificing an Overlord at the very beginning of the game, by sending your first Overlord towards your opponent. This is the only way to be able to have an Overlord by your opponents base by the 5:30 - 6:00 mark.
Oftentimes, Terran will wall off their ramp, build their buildings away from the ramp, and keep only a Marine or two by the ramp, so that your Zergling scout does not see anything useful. In addition, your opponent may keep Marines patrolling the edge of their base, to spot and shoot down your sacrificial Overlord before it can see anything.
In the event that all of your scouting attempts are denied, you'll have to make a decision:
- guess at what your opponent is doing, and prepare for a specific build (or set of builds)
- try and prepare for every type of build that your opponent might do
Knowing your opponent, knowing what strategies the map favors, game sense, and map position can all play a part in helping you here.
- Roaches or Banelings can be used to quickly break down Terran wall-ins in the early game.
- 2 Zerglings defeat a Marine. However, Zerglings alone cannot defeat healed Marines.
- 2 Baneling hits kill a Marine. The attack's splash means that Banelings are increasingly effective against clumped Marines, when a pair can kill 10 or more Marines.
- Mutalisks are very useful for harass. It takes five Mutalisks to one-shot an SCV. Keep your Mutalisks alive and be sure to fly away when the Terran brings in their marines. You will need Banelings or Roaches to deal with them.
- Ventral Sacs and Pneumatized Carapace are more efficient than Nydus Worm in terms of cost, and Overlord drops aren't audible across the entire map.
- The Brood Lord and Infestor make up one of the strongest late game armies against Marine/Tank compositions. Fungal growths can keep Marines and Vikings rooted at a safe distance while Brood Lords act as late game siege units.
- There are currently two standard compositions in ZvT: Zergling/Baneling/Mutalisk and Zergling/Infestor. They each have their strengths and weaknesses and choosing the right composition depends on the map, the play style of your opponent, and personal preference. Mutalisks allow almost complete map control and can shut down drop play, but are extremely fragile units. Proper Marine micro against Banelings leaves your army extremely vulnerable. Infestors are extremely effective against Marine/Tank/Thor compositions: Fungal Growth can eliminate Marines cost effectively, Neural Parasite can neutralize Thors, and Infested Terrans can abuse the friendly fire of Siege Tanks. However, spending the majority of Vespene gas on Infestors rather than Mutalisks effectively sacrifices map control and leaves you open to drop play. Large numbers of Zerglings are necessary in order to maintain a mobile army that can catch drops.
 Zergling Backstabs
By constantly controlling the Xel'Naga Towers and having good creep spread, you can see the moment that your opponent moves out with their army. By keeping a group of Zerglings separate from your main army or bases, you can run in behind the army and attack. Your priority for backstab attacks should almost always be SCVs. If you have a large group of Zerglings (more than 20 or so), split them into 2 groups and attack both of Terran's mineral lines.
 Burrowed Banelings
Burrowing Banelings to act as 'landmines' against the Terran army is a great way to maximize your Baneling damage. Since it takes 2 Banelings to kill a Marine, they are usually burrowed in pairs.
A more comprehensive guide on using burrowed Banelings is available here
 Dealing with a Planetary Fortress
In general, it is not recommended to attack a Planetary Fortress head-on with your army. Planetary Fortresses have 1500 hp and high armor (3, compared to a Command Center's 1) and have a very strong attack that also deals heavy splash damage. In addition, it can be repaired, and unless the Terran player hasn't saturated the mineral line, there will always be many SCVs nearby to help repair. Lastly, doing an Attack-Move command into a Planetary Fortress will cause all your units to target the Planetary Fortress and ignore the repairing SCVs. You will have to manually tell your units to kill the repairing SCVs, which, depending on what units you are using, can cause overkill and pathing problems.
There are a few ways to deal with a Planetary Fortress:
- Banelings - you'll need 20 Banelings to kill a Planetary Fortress (slightly less if you have melee upgrades). You should send 1-2 Zerglings slightly ahead of your Banelings so that the Planetary Fortress will shoot them instead of your Banelings. In addition, you should first move your Banelings into the mineral line, so that when they detonate they also kill any mining SCVs there. If you are ahead of your opponent on economy, then this is a good tactic, since it will instantly kill the base and any nearby SCVs without giving your opponent a chance to react. However, if you are not ahead on economy, you need to be prepared for a counter-attack, since you just used 20 Banelings without killing any of the Terran army.
- Mutalisks - since a Planetary Fortress cannot attack air units, this is the safest way to kill a Planetary Fortress; however almost all Terran players know this and build several Missile Turrets by their Planetary Fortress. Thus, you must have enough Mutalisks to be able to kill the Turrets (even with repairing SCVs). This will be your primary method of destroying Planetary Fortresses when using a Muta/Ling/Bane strategy.
- Brood Lords - Since Brood Lords outrange Missile Turrets, they are even better than Mutalisks at destroying Planetary Fortresses cost-effectively. However, since a large portion of their DPS comes from Broodlings, they are slower to kill the Planetary Fortress and nearby Turrets than Mutalisks are.
- Using a combination of Zerglings and ranged units - by surrounding the Planetary Fortress with Zerglings you can prevent nearby SCVs from repairing it long enough to destroy it with the rest of your army.
- Using Ultralisks - Ultralisks are specially equipped to deal with Planetary Fortresses. They have extremely high DPS, and in addition they cause splash damage, so while attacking a Planetary Fortress they can also kill any nearby SCVs. Lastly, they are big units, and so only a few of them can cover a large area around the Planetary Fortress and prevent SCVs from repairing it.
 Early-Game Banshees
- One Banshee takes 1.5 Queens to safely take down, so do not fight a Banshee 1-on-1 with a Queen. One Spore Crawler can defeat two Banshees head on.
- The common early-game defense against Banshees is to make at least 1 extra Queen, place a Spore Crawler in the mineral line of both of your bases, and then make an Overseer once your Lair completes for detection.
- Vs 2 Port Banshee, make more spores then usual, make Queens as usual and just hold it at bay until a Lair and a Spire completes for Mutalisks. Typically this build is indirectly scouted by seeing two very fast gasses taken. The key to 2 port Banshee is doing a ton of damage or winning the game out right. If defended correctly then Terran should be irrevocably behind and you should win.
 Early-Game Hellions
There are a few ways to deal with Hellions in the early game:
- Sim-city: using a combination of Evolution Chambers, Spine Crawlers, and Queens, wall off the entrance to your Natural. When you need to break down the wall, you can just move your Queens or Spine Crawlers to a different location.
- Spine Crawlers: Depending on how many Hellions there are, and whether they have Blue Flame, you may be able to survive with just Spine Crawlers and a few Zerglings. You can also keep some Zerglings at the top of your ramp so that you can surround the Hellions at the top of the ramp.
- Block the ramp: A single Queen is large enough to block off a standard-sized ramp from Hellions, if placed directly in the center of the ramp. In a pinch, you can block off your ramp and transfer workers to another base using this.
- Roaches: While Roaches are more expensive in terms of resources, supply, and Larvae, they are also more mobile and can deal with Hellion drops more easily. Also, depending on how early in the game you get Roaches, they can give you map control and allow you to put pressure back on the Terran.
 Dealing With Drops
The most common drop is a Medivac or two filled with Marines.
The best way to deal with drops is to see them coming ahead of time. To do this you must have your Overlords spread around your base in the path of possible drops, and then see the Medivac incoming in your mini-map.
When a drop comes, if you have Mutalisks out, then target the Medivac with the Mutalisks while engaging the Marines with your ground units. If you do not have Mutalisks, then target the Medivac with your Queen.
It's generally not recommended to leave a large standing army at your bases to deter drops. At most, you should leave a few Zerglings or Roaches at the most likely drop spots.
It's also not a good idea to bring your entire army to deal with a drop, since that leaves all of your other bases vulnerable to multi pronged drops or harassment, and also lets Terran move forward with his Siege Tanks and get them set up properly.
It is extremely important to begin positioning your Overlords in the early-game and mid-game in two positions:
- Around the edges of the map. Here, they provide vision to spot incoming Medivac drops. This vision is crucial to responding to the drop before it can do real damage.
- At potential Terran expansions. These notice when the Terran claims a new base. Additionally, the spotting Overlord can drop creep, delaying the Command Center.
 Late-game Defense
You should be building at least 3 Spine Crawlers at every base late in the game against a Marine/Tank/Medivac Terran, to help protect against drops.
- Use Mutalisks to take down Medivacs to prevent drops.
- When a drop is landing, you want to pull ground units and Mutalisks to deal with it. Engage with your ground units first, then target the Medivac with Mutalisks.
- Overlord drops are the safest way to break a Siege Tank contain. Fly Overlords loaded with Roaches over the tank line, unload, and bring your other units in while the Roaches draw fire.
 Common Playstyles and Unit Composition
This a powerful combination against Terran. Siege Tanks are a huge threat to most Zerg armies, so use Mutalisks to take them out and keep up harass. The main threat to Mutalisks are stimmed Marines, so counter with Banelings and use Zerglings to otherwise occupy ground forces.
Supporting build orders:
 Mass Roach
The goal here is to end the game quickly by breaking the Terran wall-in with Roaches and cleaning up remaining forces. Zergling or sometimes Baneling support is common. The durability of Roaches means that if the initial rush fails, you still have an army to work with.
Supporting build orders:
 ZvT Builds
- DongRaeGu's 15 hatch 15 pool: http://www.youtube.com/watch?v=RImec0Z9Cgg
- Strong against Terrans who open fast Hellion.
- Allows the option to attack early to allow the player to go either macro to aggressive.
- Allows a flexible tech path.
- IdrA's 14 Hatch 14 Pool: http://www.youtube.com/watch?v=Cm220rM0XJ8&
- Also known as Muta/Ling/Bling
- Great against Marine Tank with good micro.
- Fair against 2 rax and fast Hellions.
- Excellent harassing and macro style of play.
- TL forum post detailing the subtle evolution of ZvT just up to patch 1.4.0, a must read.