Sorry but that seems like a really a stupid question. Its too broad.
Best round for WHAT?
I've yet to find a round that fails to feed/fire/eject from any of my CZ75 pistols. So if "best" is what while properly function then every factory ammo I've tired seems to do that perfectly. I've also never had a commercial grade reload fail in any of my CZ75 pistols.
Are you talking about premium self-defense ammo and wondering what is 'best' in the CZ75. Again, see above. I've NEVER had a failure of any factory ammo. That said it is hard to make an objective argument that a Golden Saber is better or worse than a HTX or better or worse than a TAP or better or worse than a Hydra Shok, etc.
CZs have a reputation of being unbelivably reliable. Look up the NATO trials that the CZ P-01 passed and how well it did and you will see what I mean.
My CZ 75 is also very accurate with just about anything I put through the pipe. Yeah some loads and weight are a little tighter than some but not by much. Just find what you and you pistol shoot the best. Me personally I like Winchester 124gr PDX-1+p in my P-01 and it shoots them just fine. About a 2.5-3in group at around 15-20 yards.
FOr some reason I have found that cz and sig 9mm pistols seem to group better with faster ammo. That seems to be opposite of what i normally find.
My high power groups best with moderate speed ammo and so do my revolvers. For some reason the faster the speed in my sig and cz the tighter the groups.
Unless you are an exceptionately good shot, even with cheap ammo the gun will outshoot you. This is one magazine from ten yards on the left and 25 on the right. For general shooting I buy the cheapest stuff I can find so this was probably done with bulk reloads.
Buy the cheapest stuff you can find and do a lot of practice. You might want to use something different for carry but the best ammo in the world won't compensate for a lack of practice.