ZoneAlarm was "sold" to McAfee and Norton. Only these two get recognized by the latest ZA firewall. All others are not (even Pc-cillin,NOD32,F-Secure or avast! are not recognized.
Symantecs Online Security Check is the same nasty thing. It tries to convience you that your current installed antivirus is not really a antivirus so you'd purchase their *cough* crappy *cough* Norton Antivirus. My recommendation? Stick with avast!. Its way better than Norton. Also if you wan't to check your PC with on-line antivirus,i recommend HouseCall or Command On Demand (both can be found on my page) instead of Norton.