well im sure 95% of registered ppl dont know how to play on islands, so there wont be clear imba. And notice that most of island maps were used before zergs started to use mutastack, so the game can be absolutely different now.
zerg players should just go random tho. picked zerg sucks, but random zerg is good. (basically problem zvp is when p opens with sair, and problem zvt is when t goes m&m. vs random correct build for p is robo first and for terran it's goliath! )
although this also depends on the map. halls of valhalla is hopeless period, and gorky is tough zvp. but paradoxxx is weirder (and much more doable), and estrella is not bad.