I was using Zeus v6 since a long time then I decided to upgrade to v6.34...
I wiped everything (data, cache, dalvik-cache, battery stats, etc...) and fixed permissions, all that stuff, then tried installing Zeus v6.3 + update (tried N and O versions)...
Now it's stuck at LG logo, but at I can still enter CMW Recovery to install another ROM.
It's a shame, I really wanted to upgrade... I used the search button and someone else had the same problem as me (look for LGp970Owner posts).
Edit: I don't know if it's related or not but when I try to install it unpacks pretty fast, less than 10 seconds actually... I installed Boype's ROM after and even his (100MB) unpacked slower.
Edit2: Looks like I have solved my own problem. The fix was to install the ROM and the update two times each or it doesn't copy files. Does anyone has any explanation for that?