Zerg is a hard race to defend with. You need the creeps and the sunken colonies are SO DARN WEAK! So what you gotta do is build a LOT of them. It could get crowded, so organize them by the first line buildings at the entrance, the second at the middle, and the 3rd right be4 ur hatcheries and stuff. These work especially on those zealot rushes, and one time I never lost a sunken while defeating all of them! Try it! It works!