I also in that same other thread made a recommendation that I am about to make here, as well…
You currently have access to all of your personal files, at least. So, I would recommend backing them up and saving them on a different drive- then reinstalling Zorin OS.
What happened to you has also happened to me before- I used sudo apt remove on a package that took the Zorin OS desktop with it. And… I have done this more than once in my time using Zorin… 
The first time, I recovered by dropping to prompt and reinstalling zorin core and zorin desktop as we tried above. The second time, I reinstalled Zorin.
Since we lack confidence in What Is Missing, I think your best option is to back up your personal files and reinstall Zorin OS and get a good solid fresh start. And this way, at least, we did some good by getting access to all your personal files.