Sorry folks, but I've been away for family medical issues. Anyway, I've listened to Zinman's finale just once, and that was on my car stereo, which isn't the best. But I thought it was excellent. While Zinman's now eschews the electronic enhancement of his hammer strokes (just 2), they still sounded huge. Tempo relationships all made perfect sense, and there was plenty of forward momentum in the final allegro "charge" episode (starting after the 2nd cowbell episode). I like how he handled the last 8 minutes of the finale very much. It seems to me that Zinman very much trusts all of Mahler's own fine details written into his revised score, which is in sharp contrast to Janson's "I know better" approach to Mahler 5.
I can't really comment much on the cowbells because I was listening in my car. The deep bells, on the other hand, had a very distinctive sound. I think they may have been the same set of bell plates (or large bells) that you hear at the start of the choral "bim, bam" movement of Zinman's Mahler 3. Anyway, the deep bell sound didn't come from your usual rolling rack of tubular chimes - they're holy doorbells, at best.
I hope to listen to the first movement this morning.
Barry