About a few years back, I installed ZoneAlarm and avast says it will interfere it. I’m thinking of downloading Comodo and will Comodo interfere with avast?
No. avast has a correction for the payed version of ZoneAlarm. Comodo has not such problem.
Of course, any firewall could interfere with the antivirus and vice versa, but we can troubleshoot this, if it happens in your computer.
Welcome to avast forums.
I run Comodo and Avast on my PC without problems at all!!! 
Thanks, Comodo works fine on my computer. And why my e-mail address is showing? I selected “Hide”?
Only you and the administrators of the forum can see your email.
Since I stalled Comodo all is well but my avast resident protection settings keep changing to “custom” after I turn on the computer. But I don’t suspect anything fishy…
Sorry I know the culprit, I moved the Script Blocker from Standard to Custom by accident. 