ZM4 drop rates

ReTeNaM

Hi everyone,
I was wondering. Are there any official drop rates posted for rare card drops? 
From bosses but also from random zombie drops. Saw few 5* cards drop from zombies in a video. Trying to push stage 2 (started recently) Can for example 5* Bolt drop from any 4* or just from certain 4* bosses?

13624030065

There's no official drop rates posted. Base on my experience, 5s bolt drops from all boss from: bolt zone, lilith zone and underground (ZM4 1.0 Bosses)

ReTeNaM

Thought as much. Sadly no real info for newcommers (people that started ZM4 recently) Personally didn't play much ZM lately so catching up is kinda messy. I guess 5* cards that come from pieces (from 4* boxes) are 1 time use only as well, right?

13624030065

yes