So there it is, the first (AFAIK) freely available G-Code to ZCode converter:
Download from Dropbox https://www.dropbox.com/sh/cgt3evjontdbpjm/AADYV5T384EDeFjAgKgIB5kha?dl=0
Slicer Profiles: https://www.dropbox.com/sh/tmv5imtvw120r5b/AADyGH0L23Jfq8k0qyVntXdTa?dl=0
There is a manual (g2z.rtf) and a folder with profiles for different slicers included ("profiles"). These profiles include necessary settings and start/end codes, so use them as starting point for your own ones instead of starting from scratch.
Currently there are basic profiles for S3D, Slic3r, Cura and IdeaMaker.