Sorry I'm so late in replying, but I've been away from the software for a while. The Zoom instructions specify that the unit be set to MIDI, and that used to work. I tried the other two settings -- Internal and Remote -- and neither one worked. I'm wondering now whether there's some hardware problem that's developed in the unit, as opposed to a problem with my PT settings. Anyway, thanks for your feedback; it's appreciated. Worse comes to worst, I'll just start playing the drum parts with my fingers, using the Zoom as an electronic drum. I guess, in a way, that'll make the songs more authentic, at least minimally.

BTW, here's a link to the Zoom manual, if you care to look at it:

http://www.samsontech.com/site_media/legacy_docs/MRT3-manual.pdf