Can you be a little more detailed, how can mozilla firefox block the SafeZone Browser ?
The SafeZone Browser has nothing to do with firefox, it is a stand alone browser (now based on opera I believe).

The only thing that I can thing you may be talking about is the avast Browser Security add-on A.K.A. the Avast on-line Security add-on for firefox (AOS).

What avast version do you have, the latest being 17.3,2291 ?
What firefox version are you using ?

The Web Shield covers browsers from internet malware.