If you cant move them you can put a barrier up or just let nature take its coarse.. It may only kill the ones it can get at or even take years before it get big enough to kill them all. The zoas may spread fast enough to out run the other coral. Who knows the zoas could win.. In my coral biology class we had to document two corals fighting by moving two corals together and right up a report. What bothers me though is Allelopathy, I have some sever Allelopathy going on in my tank at the moment, I have corals that are almost a foot from any another coral fighting corals that are not there. I just can not figure what coral is causing the issue. Allelopathy can build up in a closed system and even though a coral is not right next to the other the other corals in the tank can be affected.