I really like Zorin OS and I think it is the best operating system for people coming from Windows.
I would like to participate in supporting it financially and I have read that I can install a "licence" in many computers for private purposes. However, I would like to know if it is possible to have a discount/promotion for those who have bought Zorin OS version x and want to upgrade to version x+1.
This forums are not an official support channel, and the developers only occasionally drop by. I would suggest contacting them directly using the email address provided to you when you purchased Zorin Pro.