Thank you for your question, at this time there is not a feature to change the zoom % permanently in Firefox for Android. There is an option in Settings > Display that allows full-screen browsing when you scroll down a page. There is an add on that shows to always zoom in Firefox for Android, is this something that you are similarly looking for? *[https://addons.mozilla.org/en-US/android/addon/always-zoom/?src=search]