Soft corals generally grow faster because they don't have to build a skeleton. As far as zoas are concerned, in ideal conditions, some spread very fast, and some spread very slowly.
The cheap Indonesian ones like eagle eyes and dragon eyes spread quick.
Just a word of advice...don't put anything in the tank you don't love to look at. I see many people adding kenya tree and things like that to their tanks and while they spread like crazy, IMO
, they are quite ugly, and hard to eradicate, when you get tired of it.