I am running:    ZoneAlarm Firewall (only 1 firewall enabled)  Avast! Free Edition  Malwarebytes Anti-Malware (paid edition, w/ real-time)    I am also using Firefox, with the WOT safety plugin.     Is this good security? Or can it be improved?

_____________
ciasto z sezamem
Przepisy na ciasta
Å,atwe ciasta

I don't think you need further improvement. What you need is to be updating the outlined softwares on regular basis as soon as it becomes available to their respected vendors.
You will be just fine.

I agree with with what Perfect said. I want add that it depends on what you want which the features of the above softwares must have guided you.