Disclaimer: I am not responsible for any harmed corals.
I think the zoos will be ok.
How close is the hydno to the frogspawn? The frogspawn and hydno may fight as they both have sweepers, but they may be fine. Keep an eye on them.
Here is how close the other corals are to my hydno. They have been growing together on this big rock for several months. I am more worried about the zoos overgrowing the hydno than the hydno hurting the zoos...