For zoning you'd usually use the WWPN (World Wide Port Name) which is assigned to a single port. With a single port HBA you have one WWN/WWNN (World Wide Node Name), and a single WWPN, and for multi-port cards you will still have a single WWN/WWNN but multiple WWPNs, which may be used for different zones. (maybe World Wide Port Name - Wikipedia helps)
André