Yeah, I can post my recent reps, I've had a pretty heavy losing streak as random due to consistently getting PvP and TvT (zomg so bad at them), so I switched to zerg. Got myself out of a 6 loss hole back to 5050 in 7 games as zerg.
Let me point how how the dynamic of Zerg, in my mediocre gold league perspective, works. I feel as I have a very innate advantage that comes out of a early expansion (really, as far as ladder goes, just 13/14 hatch every game, the few games you lose due to cheese become a statistic, a acceptable risk). THEY need to respond to this, because while I have an innate econ advantage, I have an innate tech and army disadvantage. Zerg however, can quickly muster up an army, and can transition tech the most easily.
Your measure of success is how effectively you can retain your strategy despite their adaptation. Their measure of success is how well they can adapt, and force you to adapt. (this excludes ZvZ obviously)
Heres a basic summation of the matchups.
In ZvT, the optimal build is going Zerglings/banelings after a early hatchery. Some people expand as early as 13, others wait until a safer 19. Its personal preference. Unless you want to run a riskier strategy (don't want to say cheese), to say, baneling bust if they're hardteching, this is what your going to adhere to every time.
They have several options. Doing nothing is not one of them. If they play "normally", you simply outecon them. If they go heavy marines, kill with banelings and mop with zergling and mutas. Tech to broodlords while expanding over half the map, containing them with heavy muta harass and banelings. I've never lost this MU if they don't adapt. You simply steamroll them.
This is the same with ZvP. They need to react. Without reacting, their is simply no way they can win.
They need to react. Its all about predicting how they react and defending accordingly. A hard early push with MM army is the prefered option. You need to outmicro them with zergling/banelings. If they don't send in heavy harrassment, assume a tech to banshees and react with AA or straighttech to mutas. If they're smart, they'll try and make you overinvest into zerglings/banelings and kill you with upgraded hellions. Predict and add in roaches. If they early expand, you need to either take it out with early zergling/baneling/roach push, or take a early 3rd expansion.
Your success is measured by how well you defended your additional expo. A flawless defense is a easy tech to mutas, containing them with banelings, and securing a rediculous econ advantage, or just winning. A flawed defense means they've successfully negated your advantage. They've delayed mutas to secure their own expo. Your going to have to match that. Or, likely, a extremely well timed push will simply end the game. If they time their MM push to catch you off guard, without at least 4-5 banelings, it can often be GG. If you've overinvested in zerglings, they'll wipe the floor with you using mass hellions, timed right before mutas come out. And if you've failed to tech fast enough, they'll get you with banshees.
Similar story versus P. They'll pressure you to over invest in roaches, undertech, and kill you with immortals/stalkers. An early 4 zealots can deny a expo outright. Mutas are subpar, roach/hydra is better, and your success is once again determined by how well you stick to your plan. Their going to try to time their pushes during weak spots. You need to fill in weak spots.
(As for ZvZ I just win all my games going a build outlined below at TL. Also its nice because it opens the same as my normal build so It doesn't even matter if I fight random lol
http://www.teamliquid.net/forum/view...opic_id=117763)
Perhaps react was a bad word choice. Zerg are the most reactive race. What you aren't is proactive. You will almost never need to stop THEM from doing something. They will be constantly try to stop you, all you need to do is react accordingly.
Here are some replays from recent games. I'm bad, and I just got back from a 4 day trip to Boston (sadly not PAX related

), if you think you could benefit them. I think theirs one lost in their, I haven't played too much since the patch, and I thought he was just trying to catch me off guard with banshees. I wasn't expecting heavy investment, and their strength surprised me. I could have won easy with more hydralisks and less roaches.
Or if I had been less retarded and hadn't spend 20 seconds looking for where I put my overseer xD.
http://www.megaupload.com/?d=CPU6YGXS
(Hope I'm not too bad and I didn't waste your time with those replays...I'm hardly the kind of player who could be teaching other people through the sharing of replays lol)
That being said while I like what the Zerg macro mechanic does, I think its the most retarded. Why doesn't my queen just automatically cast it? lol. I'm not going to be casting it on anything other then a hatchery, and the confliction with creep tumors (you only need 1 :/) isn't enough to warrant disabling it :/
At the very least I think they should put transfusion and spawn larva into one spell, nerf it, and make it so it heals ~90 when cast on units or nonhatchery buildings.
A little bit back on topic, yeah, I really can see how Z are the most mundane race to play. They rely on adhering to their strategy and adapting it as they go other races are based around proactively deciding a strategy to play in order to counter yours. They need to be the actors, you are a reactor.