Ok, I've managed to install Zimbra inside a illumos (SmartOS) LX zone.
I'll perform more tests, but everything seems to be fine. I had to perform some modifications, but in the end...it works. I might even make a script to do it.
Why? Because I can. Should I put it in production? Probably not. At least, not for now. But it's nice to see it's possible to do it!