The ports that you mentioned should be the only ones needed for the integration, but just to confirm, you turned on the Zoho integration from under /dom_crm.htm and then from under the user portal correct?
Both had a green check mark next to it? If yes, then from the PBX's end the integration was done.
You can then turn on the admin level logs for , "trunks", "CRM Related events" and "call messages" to the highest and make the call and see if there are any PBX related issues.