i get it.
i love zoas as well, it's just not a reef tank without some really cool button polyps...
zoas do like high flow actually, they just grow differently... they have smaller but greater number of polyps, more focus on total colonial expansion rather than individual polyp growth, they stay small and close to the mat.
i think this makes them actually grow slower, but for certain ones i think they actually look a lot more beautiful... it seems like it's a lot easier for them to grow big polyps and expand more in lower flow tanks... and you will definitely have to isolate your SPS from your zoas/palys, they will encroach and choke out your sps for sure...
i suggest putting them down low in the tank far away from the SPS... also a good idea is to put them on rocks isolated on the sandbed so they can't spread beyond their "island"
granted i dont think they are as big of a concern as far as encroaching as compared to something like xenia or gsp but they are definitely a concern.