It's not true that avast! crashes when it's used with ZoneAlarm on the same computer. You said you're more used to Zone Alarm than avast!... strange.. ZoneAlarm is not antivirus, but software firewall.
I use both, ZoneAlarm and avast! and it makes perfect combination. They like each other very, very much
Ask other users, members of this forum that uses ZoneAlarm and you'll get same response...
Sometimes it´s not possible to uninstall avast! antivirus standard "ADD/REMOVE PROGRAMS control panel" way. In that case you can use uninstallation utility called AvClear.
You can download it here:http://www.avast.com/i_idt_1336.html
NOTE: Read instructions prior to using that tool !