Zeo has nothing to do with flatwormStop, and no, I haven't used it. As Proteus said, it doesn't stop them, just slows them down. Using it for no reason sounds expensive, and I think the money is better spent on dip and a magnifying glass. Dipping all incoming pieces, every.single.time should avoid them. I go them because I missed dipping a couple pieces that I shortly after realized were infected. I thought I'd got the affected frag out in time, but apparently not
As for losses, I've only lost one full piece, and half of another. So far no other coral has shown them after dipping.