Need help in 2's. PPv?Z

My friend and I have clawed our way up to Plat and we seem to be stuck there for now and seem to be having some issues when it comes to playing against a single Zerg opponent.  We play as double P which we know sucks very early so when we lose to zergling rushes backed up with marines or zealots we kinda just toss those games aside.  The problem comes with we have no clue what the heck to expect since they can transition so easily and we need completely different units depending on what they built.

When we try to be aggressive they use lings as blockers and surround us while MM get free shots in.  When we sit back they have mutas out at like 10 minutes (we saw them at I believe 7 or 8 one game where the 2nd player fed the first resources) and since it's 2s they can OVERBUILD mutas to run around and rip up our bases while his partner has the main army or use ling runbys every time we move out but we can't wall off to defend it because if we do then his partner does a drop and we screw ourselves with the walls.

We seem to win more when the Zerg actually decides to go roach instead of muta/ling since roaches are alot easier to blow up with immortals and sentries than it is to avoid sling surrounds with a 2nd army shooting at you.

If we fight PZ we have been going 3gate/Robo-3gate/Stargate and using Phoenix harass to keep them back and keep them from going muta and handles any normal P build. 

So does anyone have any suggestions on what we could try to do or what you have found that works for you?  Keep in mind it's 2s so it's whole different kind of cheesy world