Anyway, thanks for the all the help. I have left the DNS as it was in my last post, changed the hostname to be on the base domain without the 2 subdomain nested, removed the public IP, and removed and reinstalled Zimbra. All is working well now.
If anyone else runs into an issue with 0.0.0.0/0 being a trusted network, it is a default setting because I had my public IP an on interface with a /32 address. Personally, I think it should be ignored as an exception, as making postfix is open relay is never want you intend to do, and shouldn't be default, but 0.0.0.0/0 was a network I was joined to (because of the /32 IP).