Well, I have a printer very similair to the z615 (its an X1150 - basically a 615 with scan and fax).
The driver for the printer works, but it expects old cups versions and may have some problems on Debian (I cant say as I installed on Gentoo, and have barely tried on Arch) The install walkthrough for Gentoo is
here. I would suggest that you make an attempt to install the driver before you purchase the printer, as installing the driver (at least in Gentoo) was quite a chore and wasn't exactly certain to work.