I haven't modded my CZ...yet. But when I did the Trigger job on my Hi Power I had to change four springs. The trigger return spring, heavier, The recoil spring, heavier. The firing pin spring, lighter. And the trigger spring lighter. but it's much nicer now, I ditched the magazine disconnect at the same time. I was told that they all work together and it's the way to get it done right. I was worried I'd never get that gun put back together as there were parts all over the place. It all worked out with no parts left over either!
HOWEVER Neither the CZ or the Browning's trigger can hold a candle to my new Fusion Reaction 1911A1. 4lb 9oz and the thing is smoother than butter coated with Teflon. Of course it cost more than the both put together.