Well if they have grown towards each other naturally there isn't much you can do about it
It's possible they will get used to each other and things will be hunky dory. Or the polyps may irritate the edge of the favia colony and cause some tissue recession, or the favia may sting nearby zoa polyps causing them move back.
Sorry it's not 100% answer, but that's kind of the way it happens on the reef also, corals overgrow each other, sting each other etc all in competition for prime space for light and flow.