Get underneath a leading edge, and you can peel them up off the rock, then run a razorblade down the mat in between the polyps. Once you have a section of them, use a little bit of some gel super glue to attach them to a new rock and put them back in your tank to heal for a couple weeks.
One caution, however..... wear rubber gloves and safety glasses, and do NOT rub your mouth, eyes, nose, or open cuts until the gloves are off & your hands have been washed.
Some palys/zoas contain a poisonous compound called palytoxin, and it's some pretty nasty stuff.... problem is, we as reefers don't know which ones contain it, so it's best to treat all of them as if they have it.....
Palytoxin, the World's Second Deadliest Poison, Possibly Available at Your LFS — Advanced Aquarist | Aquarist Magazine and Blog