I was too lazy to uninstall (in fact, to reinstall after uninstalling) ZA until now because it doesn't allow to export settings (and because Comodo works perfect on other computers with ZA). I made this effort today (and removed everything I could with ccleaner and regseeker, cpes_clean.exe doesn't work on my system, the process closes after one second) but this has changed nothing.
I don't know what initialization is done when CIS installer is run, but the fact that the window asking the language is skipped and the main installer windows is shown without text make me think about a potential problem with OS language settings. I've checked that the configuration on my main computer is the same that the one of my other computers.
Now I made the effort to remove ZA, I wont reinstall it, so I've installed PC Tools Firewall for now, but on a first touch I really prefer the look&feel of Comodo (more clear, more advanced) and I like Defence+.
If this problem is not corrected, I'll have to wait my next OS installation to try again, and I've no installation planned (too many work).