My experience has been that keeping your phosphates as close to 0 as possible and dosing iodine really helps zoas and palys grow.
I dose lugols iodine once a week per the directions on the bottle.
Honestly I do nothing special and I have tremendous growth in all of my zoas and palys. I use T5 lighting, 3 different spectrum bulbs, and do monthly water changes. It may just be luck.
i had luck with vitamin C for health when i kept zoas and palys. they also seem to like to eat/sit in detrius every once in a while as long as your p04 is low and your nitrates are below 20
EDIT: they don't do well for me now and wither way under my low nutrient sps system
^ good point. i used to take a sharp, clean razor and slice the webbing between the polyps of zoanthids. i think it makes them think they're all alone and motivates them to reproduce. that worked very well for me
Flow is very important. Most like to be moved by the current. Less flow = less growth. Mag levels are important as well. Feeding Palys and PE the Hikari Mysis (They are smaller than most mysis brands), and Cyclopeeze to the other zoas.