No, no, no... I have only respect for Zappa; it's a superb and highly original piece of software. I have no idea what you've done with it, but it certainly plays chess.
I tried it on an Intel dual in UCI mode -- it didn't run properly. I set it up as UCI under the Fritz GUI but it crashed when I tried the Marathon tactics test. It crashed too when set up as a WB engine too, with 2 threads... Therefore I've been using as single with no glitches.
Zappa is currently leading against my engine 5-4 and is certainly more than 1610 can swallow, at least for the time being
King safety is an issue though, as you duly remarked (1610 diced it up soundly a couple of times). Still, my engine is a punching bag at times too, so I'd better keep quiet.
Thanks.