I feel ZvP is probably in favour (slightly) of Zerg at the moment actually. It's just that we don't struggle nearly as much versus Terran (but it's still very, very tough, you _have_ to be a better player than the Terran (or get lucky), to win). ZvT is basically doesn't matter if you're a better player, the odds are the Zerg is going to lose.
ZvP, the problem is map control. In order to get the hahah I win death ball (mass stalkers, sentries, 4-5 colossi), you have to give up map control and suffer pretty insane muta harass. If you can survive that, and get your ball together, the Zerg is running anywhere between 3-5 bases and roach/hydra your deathball, die, then follow up with infestor, ultra.
You can't out macro Zerg because you have nothing that can stand up to hydras. You have a window early game and if you don't do some damage there (10 supply, 2 gate pressure), you're probably going to lose against a good zerg.
There's one build I worked on last night which works against this muta ling into expo, mass expand, but it's an all-in and if scouted fails miserably. There's no real stable build to give you mid game parity with Zerg at the moment. And it's that midgame period that's really tough vs Terran too actually.
I guess the problem I have as zerg is each game against non-zerg races is a gamble on what tech to use. On most maps your enemy will get a tight wall off... By the time your Overlord has reached your enemies base you have already had to start making tech decisions as Zerg. Gamble wrong and those decisions are worse than worthless they are crippling. Bot Terran and Protoss have decent core units Terran : M&M Toss : Stalker Sentry Zealot
These units will do you well against 80-90% of enemy strats, all you have to do is adjust unit production to suit, whilst building your next tech level. - These are all tier 1, 1.5 units. All zergs tier 1/1.5 units are are meatshields. The baneling become more of a nuisance / distraction against terran (unless they go mass marines) and are not that useful against Toss.
Zerg early game is practically an all in:
Make too many drones - Die to early aggression
Fast expand - crippled by early aggression
Make too many units - Have too weak an economy to keep up
Mass Lings - Die to zealots/Marines/hellions
Mass Roaches - Die to marauders/stalkers/air.
Get to mid game. see enemy has a lot of X units
Make Mutas. - Hope he doesn't attack before I have 8 + mutas
Make Hydras - Hope he doesn't go Colossus/tanks/mass carriers/mass BC
Late game "I usually win \o/" - Unless its on Kulas Ravine
At the moment My match-up preference is :
Zerg - Ballanced game best player will win. I'm quite comfortable in these matches, and feel like I win most of them (where the enemy doesn't > 9 pool)
Terran - Most Terrans I am playing at the moment are stupid. If they were any other race they would be bronze maybe silver level players. but because they are terrans their All in strats probably give them a positive win: loss ratio. But I'm fairly good at spotting all ins. I'm winning about 60-70% against Terran (currently. And each loss feels like I have lost not because I was outplayed... But because the race was better than mine)
Toss- I hate playing Toss. These players seem to be about the same level as me (maybe a bit lower in skill) but they just have the right tools for the job and there are some quite clear anti-Zerg builds that will put a lot of preassure on Zerg. If I get to the late mid game (i.e. start researching hive) I am usually in good shape. But up until that point I simply do not have the right units to fight Toss.
. getting lot better at P now won 9 games in a row yesterday 
