I had already tried Gnomad2 without success but decided to try it again only to find it wouldn't load. Eventually traced the problem to the wrong version of libmtp. I had 0.2.4 and the only version that Gnomad2 would work with is 0.1.3. So I emerged 0.1.3 and Gnomad2 starts but fails to recognise the Zen. It's strange because the Zen comes up as docked. With mtp-detect I get this:
Autodetected device with VID=041e and PID=4157 is UNKNOWN.
Please report this VID/PID and the device model name etc to the
libmtp development team!
PTP: Opening session
PTP: request code 0x11e6a8 sending req wrote only 16 bytes instead of 0
PTP ERROR IO: Trying again after resetting USB
PTP: Opening session
Could not get device info!
Connection error.
No devices.
And that is, presumably, because I now have an old version of libmtp

On December 28th. I managed to get the zen detected with libmtp 0.2.4 but it was at that point I decided to stop worrying about it. I have to keep XP on my system at the moment and it's far less hassle to update my Zen by rebooting into that (I don't use my zen much so it's only a matter of about once a month). It was my own fault for buying a piece of hardware without checking first!
Self-righteousness is a loud din raised to drown the voice of guilt within us - Eric Hoffer
Don't believe what it says on the right - I am anything but sagely; More oniony!