When I play 2v2, I play super aggressive with my Zerg, putting early pressure and try to contain them and get map control for as long as possible with lings or roaches, then let my teammate get his units and whatnot up.. Getting units for map control doesn't have to be 10 pool or that sort, just early enough units to hold the xel naga towers and maybe some harassing or runby..

Using zerglings give you more mobility and map control as well as always giving the looming threat of a runby, causing the opponent to go out of their way and get a lot of defensive structures or units..