Out of nowhere today, the appearance of Zorin has changed to what I believe is the default GNOME configuration, whereas previously it was running the default Windows-like appearance. I can also not change the appearance back, nor can I set the configuration via the GUI to allow icons on the desktop.
In my efforts to fix this issue, I've updated all the packages on the system, tried reinstalling the Zorin desktop, and upgraded from Zorin Core to Pro. Per another forum post, I also tried updating the mesa-GL drivers. There are two configured user accounts on the system and both are impacted, so it's not a single user profile issue.