I think we all know, at this point, why the 256SHA does not match and why you cannot install it.
Downloading Zorin OS from any other site than the one provided by the ZorinGroup is risky to say the least. Who knows what changes were made to the .iso or what malware could be added to it?
As you asked above, Zorin OS Pro contains some perks, but is primarily a means of Donating to Support Development. Zorin OS is not Microsoft - it consists of Two People doing all the work, full time.
Donations made by choosing Zorin OS Pro fund the project and keep it going.
But Zorin OS Core is free and contains all the same functionality and performance as Pro. There really is no need to try to get a copy of Pro elsewhere.