If you install Gnomad, restart hotplug (just in case...) and plug your Creative Zen V, Gnomad won't find it. The gnomad ebuild is lacking libmtp as a dependency (could it be activated also as a USE flag for being optional?), so devices that work with that protocol won't be seen by Gnomad.
Steps to Reproduce:
1.Plug Creative Zen V.
3.Gnomad doesn't find any device.
Find the device.
Once libmtp has been installed and Gnomad re-emerged, all worked correctly as the configure looked for & found libmtp.
The gnomad version that you tried this with didn't support libmtp. The current version in portage does.