I love OTL amps with most high impedance headphones, including all ZMFs. I've been pretty fortunate having owned a legendary amp, the Glenn OTL and another amp that unfortunately less than ten people on the planet will ever own unless something changes, the Airmid, which I like so much that it made me sell my GOTL. Ive also owned the WA2 as well as the La Figaro 339, both of which are nice sounding amps.
While many amps can sound good with ZMF headphones, OTLs are the only amp type I've heard where a near religious experience can be had. The right music, the right pads and the right tube roll can bring the wow factor unlike anything else ive heard.
Last night I dropped a different rectifier into my DAC and a different pair of power tubes into The Glacier, plugged in the Atrium, set my "Headsets" playlist to shuffle and knew immediately that I had a winning tube combo. Fire on High came on and it simply rocked my world. Fantastic mids, incredible texture, goosebump raising staging, and deep, tight hard hitting bass.