Deleting SuperAdmin Email?

I changed the default email for my super admin account. The other email has become a secondary email, but I want to delete it. How do I go about doing that??? Do I have to close the account, and sign up for zoho again? (I don't want to do that.) It used to be the super admin email, but now I don't need it. I'd like to make it a group email, but it's not letting me do that.