I don't usually see any problems with zoa's and leathers come in contact, but my Figi has never been a guine pig on this one.
I wouldn't worry, but just keep a close eye on the leather. If you see the area where the zoa's are coming in contact look ; irritated, lacking polyp extension relative to the rest of the colony, or developing any sign of black neucrotic tissue - then move em quick. Unless you see any of the above, I'd bet they will be fine.
Also, as the zoa's move in closer they may get shaded by the leather which will discourage them from moving any closer.