General ZvZ Strategy
 Unit Roles and Counters
- Zerglings: The main attack force early on, the amount and timing of Zerglings made largely defines a players opening. They can be produced early and in large numbers to try and end the game, or in lower numbers for scouting or to delay your opponent's attacks until Roaches are available.
- Roaches: Due to the lack of a cost effective hard counter, as well as their relatively high HP and decent damage output, Roaches are the bread & butter unit for both defense and offense in most Zerg versus Zerg strategies.
- Banelings: Used commonly in conjunction with zerglings for aggressive play, usually in the early game. They are the hard counter to Zerglings and as such are the main choice against armies which consist of a large amount of Zerglings. If using mutalisks, they can also be used as a viable option in the mid game army in conjunction with centrifugal hooks to take out enemy hydralisks that are a threat to your mutalisks
- Hydralisks: A high DPS midgame support and anti-air unit used to back up roaches or defend against Mutalisks. Due to their low mobility and relatively low HP, Hydralisks are very vulnerable unless they are supported by other units, such as Roaches.
- Mutalisks: A high mobility unit used for drone harass and Overlord-hunting in the midgame. Low numbers of them are relatively weak in open combat, but larger flocks are a great danger to any unprepared opponent.
- Infestors: Vulnerable caster unit which can move while burrowed. Mainly used as a support unit in Roach-based compositions. Their Fungal Growth spell can shift the tide of larger battles if used properly.
- Corruptors: Support unit against Mutalisk-based unit compositions. Otherwise rarely used.
- Brood Lords: Slow, but high-damage air siege unit. Rarely seen in ZvZ due to their late position in the Zerg tech tree. Very good against Roach/Hydra/Infestor armies if the game gets to that stage.
- Ultralisks: High HP and high damage ground unit. Similarly to the Brood Lords, they are rarely seen in ZvZ to their late position in the Zerg tech tree. Once Ultralisk tech is available and in conjunction with Infestors and their Fungal Growth Spell, they are great options against Roach-based compositions.
Due to the volatile nature of Zerg, ZvZ is a match-up of constant scouting for the tiniest fluctuations in your opponent's play and adapting to them accordingly. As opposed to playing against Protoss and Terran, where unit and worker production mostly go hand in hand linearly, the Larva mechanic creates a dynamic where only a few drones too much on your opponent's side can open an exploitable hole in their defense which is yours to use. Similarly, only a couple of drones more on your opponent's side will give his economy a big advantage over yours if left unpunished.
Most ZvZ matches that enter the midgame are focused around roach/infestor compositions. Battles, and therefore, the victor of the game, are decided by four factors:
- Army positions: a greater concave and surround ensures maximum attack efficiency with minimum losses. Once roaches reach critical mass, individual roach micro takes a backseat to superior army positioning.
- Effective fungal growth usage: Because roaches do not have good DPS, fungal growth is necessary to maximum damage. The recent buff for fungal against armored units makes Infestors especially effective. Units that deal good DPS such as zerglings and hydralisks are effectively shut down past the midgame due to infestor usage.
- Consistent injects: In ZvZ, army production is a must once armies are traded. A player who falls behind on injections can lose a game even if they are the victor of a battle due to not having the same unit production capabilities.
- Upgrades: attack and defense upgrades can turn the tides of battles easily even if a player is outnumbered. +1 range is usually the first to be upgraded. It is ideal to stay ahead of your opponents upgrades by 1, i.e. if they have no evolution chamber, you should have one, and if they have an evolution chamber you should aim for two
- Use Overseers for scouting as well as to delay your opponent's upgrade-timings on their Evolution Chambers or Spawn Larvas on Hatcheries. Also make sure to bring them into battle against Roach-based unit compositions, in order to be prepared for burrow-play.
- Later in the game, Zerglings in low numbers can quite often become useless in larger engagements, as they are low HP and often don't deal much damage against armies with armor upgrades. But if you still have some left from the early or midgame, don't waste them and use them for economy harassment when your opponent is leaving his base or use them to deny expansions.
- In Roach-army fights, always try to get a concave on your opponent. An army with good positioning can beat an equally-sized army even if it is ahead in upgrades.
- If army sizes are relatively similar and your opponent has only a few more units than you, one or two Spine Crawlers can change the outcome of a battle in Roach vs. Roach engagements. Use them to be safe against potential all-ins from your opponent, but don't rely on them as your only defense.
- Due to the time needed to assemble a decent amount of Roaches, Banelings are the best choice against early-game Zergling-based strategies which are focused on overwhelming you.
- Roaches in turn, are a great defense against attempts to hurt your economy using Banelings.
- If your opponent still has lings around and you know about it, never leave your base undefended when moving out to attack your opponent. Leaving just three Roaches behind can stop a group of ten Zerglings from wreaking havoc inside your base while you're marching across the map.
- Roaches can be used to block ling run-bys by placing them on hold position at chokes and ramps.
 Additional Notes
- Scout continuously. Especially in the midgame, a window of one or two minutes where you don't scout is enough for your opponent to stop Drone production and produce an attacking force which you may not be able to prepare for in time.
 Common Playstyles and Unit Composition
Mass Roaches are relatively cheap, have high HP and do decent damage. The fact that they effectively counter most other Zerg units in terms of cost effectiveness makes them the main choice for most unit compositions. Infestors provide great support via their Fungal Growth spell which does 10 bonus damage against armored units like the Roach. However their value doesn't really show until armies get relatively big, which happens towards the end of the midgame, so pure Roaches will be a better choice until your armies reach 120 supply and beyond.
Mutalisks provide a transition from early to midgame that can do severe damage to your opponent if it surprises him. Since you will usually have a lot of minerals left over after producing Mutalisks, the other main component of this composition is the Zergling. If your opponent tries to counter your Mutalisks with Hydralisks, you can add Banelings to the composition, which are a great option against slow Hydralisks.
Mutalisks are rarely seen in ZvZ due to infestors being a far more economical and effective unit that can shut down mass zergling, baneling, and mutalisk playstyles.
Since Infestors take a relatively long time to tech to and then build, plus only really become a very powerful unit in towards the late game, many players choose the Hydralisk as the main supporting unit behind their large Roach army. Very vulnerable themselves, with relatively low HP and slow movement speed, they provide a great damage boost once they are protected behind a wall of Roaches.