AVG and Avast are good. I think Antivir is useless. Flunked to many tests. AVG and Avast are as good as any paid for AV Programs and I would recommend AVG over Norton.
You should only have one antivirus program and one firewall. I'm not very fond of Zone Alarm, causes drastic slow downs. I think Sygate is a better alternative. If you ever uninstall Zone Alarm, ensure you follow the full instructions
here.