I don’t have a ZMC, but I use a Cinemag SUT. I run the ground from the TT to the SUT and another from the SUT to ZP3. I have tried removing the ground between the ZP3 and SUT and get a hum. On other phono pre’s you can eliminate the SUT to phono pre ground to lower hum, I believe Steve mentioned the ZP3 needs ground to the SUT n the papers, but I haven’t read them in awhile.

If you get hum, I’ve read wrapping the ground around the RCA’s can help. Made no difference for me. My system does hum, I didn’t think it did until I turned the whole house fan off. I don’t notice hum during playback, just with my ear in front of speakers.