I would like to share a little Idea. I would find it a good Thing when Zorin could offer in Zorin Appearance an Option to customize the Login Screen. Yes, customizing GDM is ... a Problem.
But when the Zorin Crew could handle it, it would be a nice Feature I would think. Not everyone take care of this, yes. But I think it is nice to have and would make a Customization more complete.
And because Zorin already have it's Customization Tool Zorin Appearance, it would be a good Place for this Option I think. You could offer on the left Side a new Entry called ''Login Screen'' or ''GDM'' and on the right Side You would find Options like:
The most annoying thing about Zorin when I first tried it ~2 years ago was that the live ISO correctly identified my primary monitor but the installed OS did not, instead picking a portrait-rotated screen I have at the side and, of course, not rotating the image. Even after logging in and fixing that, the settings only applied to my user account, not to gdm which kept putting the login screen sideways on a non-primary display. I can't remember the exact command that fixed it, but it involved copying an XML file containing my monitor settings from my user folder to some gdm config folder somewhere.
It's an ongoing issue as someone else recently posted about a similar headache, though they haven't yet replied to my suggestion of copying the config file to see if that's still the correct solution.