nod 32 is the best A/V. kaspesky isn't that far behind. I would not messed with ZA. for one thing, it a pain to configure especially if your systems has advanced networking. also a firewall doesn't stop a virus, but it can stop a trojan from phoning home. if you must have a 3rd party firewall, use vcom system suite 7.0 which has a great antivirus with it too.
but if you have a great A/V and a few great spyware programs (I'd add spysweeper to your computer) windows firewall is good enough