Ive been blasted by Zoas before, they can fire that nasty liquid pretty far. Luckily I wear glasses and have since invested in additional eye protection. Im more concerned with bristle worms. Seems like everytime I pull a colony out to cut frags theres a damn bristle worm waiting to sting me, and Ive been stung, dosent hurt too bad, but it leaves this extremley irritating abrasion and can be very dangerous if your allergic to bees (form what Ive heard).
Ive never lost a colony form fragging, have had frags die, but no colonies and I usually cut and scrape the zoas directly off the rock with an exacto knife and glue right to a plug. SPS are fairly easy, most of them will just break, LPS can be another story. Things like favias and acans can have a very hard calcuim base and need to be cut with a dremmel or surgical bone cutters. Ive seen favias with 2" thick skeletons.