From this, it sounds like you are unable to boot into a graphical session, and that you do not know the cause of it.
If you knew the cause, you would know which files are corrupt to replace - but you do not.
And... Zorin OS Pro does not include any different GPU drivers, Graphical tweaks or anything - Even if you were sent a Zorin OS Pro .iso, you would run into the same trouble as you have using Core .iso.
To narrow this down; What GPU are you using? What specs are your computer?
There have been some rather catastrophic updates updates recently: