Expect the opposing zerg to be utilizing the same orders as you! Zerg vs. zerg is the fastest matchup in the game, and goes fairly quickly. Matches rarely take more then 6-9 minutes, so there is hardly a late game and a pretty consistent midgame. The game revolves around the air/ground trade-off – zerglings are cheap and fast to make, mutalisks can kill zerglings. Whoever gets mutalisks alone will be able to decimate the opponent's economy, so the game revolves around trying to get more mutalisks before the other player OR getting mass zerglings before the other player gets mutalisks.