I have ZoneAlarm Free and Avast! 4.9 Free.
I have compatibility issues, and tried almost every trick in the book to make the combination work.
I really don`t want to give up ZoneAlarm nor Avast!
This Iis only a suggestion for you try Online Armor Free , http://www.tallemu.com/products-online-armor-free.php There is no compatibility issues using it with Avast and its rated higher as a firewall In leaktests.
The problems is that when windows starts the computers freezes. (I have Vista 32bit). I did some research and found compatibility issues between the two.
I uninstalled the WebShield of Avast! but no luck…
ZA used to be the number one in Free FWs. However, their Free FW has slacked. OA, OP and PCTFWP have eventually over taken it. Better use either of the three.