Hello, 

As far as I know there is no guide for that, but it's quite simple to modify the Qweb template.

and to test whitout printing this website is great http://labelary.com/viewer.html
with the online browser.
unfortunatly the defaut ZPL model is not compatible to the standard ZD410 model that is recommanded by Odoo.

here a ZPL sample adapt to the ZD410 :

^XA
^FO35,10
^A0N,35,35^FB350,3,0,L,0^FDMy Product^FS
^FO35,120^BY2
^BCN,150,Y,N,N
^FD36623432424805^FS
^XZ