I've been collecting zoas for 6 years now and have a 90gal tank dedicated to them with over 120 kinds. I would say they are relatively easy to care for except for the zoas that are well known melters(Mauls in particular). In my opinion, the most important thing is to keep the tank stable. I used to dose and use additives but the one thing that has really been my key to success is a routine water change. Weekly, I do a 10 gallon water change and everything is thriving.
In terms of zoas fighting with each other, the only issue you will have is one colony out competing another for growing surface. This can result in the faster growing zoa killing or overtaking the slower growing one. Easy to prevent this with fragging though. Maybe when setting up your rock work keep this in mind so that it's easy to remove rocks to frag.
I know people love pics so here's a few