Take a pair of bone cutting pliers and trim the rock away, as much as you dare. I just try to chop off as much of the rock as I can without breaking it. If you break the rock into 2 pieces, just take a sharp razor blade to the split and cut the zoas right at the base where they are attached to the rock. Slice it into 2 frags.
Hopefully, you won't bust the rock into 2 pieces. Just trim off as much as you can and then wedge them into a pocket on some live rock. Or, set them down on a shelf and put another small rock next to them. They will spread out and grow onto the new rock. Pick it up and slice the 2 frags apart when they have spread enough.