That's a load of replays Infirm! I'll have a look over some of them later and might even be able to give advice as I've played quite a few games a s zerg.
Quango asked in another thread if I could upload a macro game, and ask and ye shall receive!
This is a long TvT on Steppes of War against a diamond ranked player. I opened with a banshee timing attack, switching into mass tank/marauder/viking. He attacks my gold expansion, but knowing that I'm on more bases than him I decide to trade bases, taking out his natural, and then I manage to win by just having more stuff than him.