Hammer and chisel. Most live rock is relatively soft. What I've done is chiseled off zoas from rocks (wear gloves and eye protection! I speak from experience!).
Or, if the zoas have spread from one rock to the other and you just want to separate the rocks, cut the zoas with a razor blade as you gently pry the rocks apart. Generally you can cut the "connective tissue" between the polyps.
sometimes i can peel back gsp but some of the time i need to break the rock. now i do what is recommended here and i lay down loose rock pieces around them that acts like a natural frag station.
