Keep in mind, some zoas grow much
faster than others. There is no hard number for propagation, since there are literally hundreds of different kinds. I have some that almost seem to pop a new head nearly every few days, and I've got one that started off as two polyps a month ago, and I now have three...... That's what makes some of them so expensive, since you get so few of them to frag.
As far as spot feeding, I only feed the corals that actively eat (LPS
& palys). IMO
, spot feeding zoas is just adding far too many nutrients to your system for the little benefit gained....