>>717636769
Mutas are good but cost a lot of gas, zerg needs to stay ahead in bases but they can't until they get drops (which costs a lot of gas), and the other races can hard counter them easily since they know zerg are forced into muta
Sparkle (the map in question) actually went too far in the opposite direction by giving too much gas and they raped terran. It's actually one of the few maps that are skewed in zergs favor in that matchup