Absolutely perfect.

good

Nice options, write your own new default zoom steps in between the big default jumps.
In the tiny list at the bottom, write your own prefered zoom levels in numbers, where 1.05 is 105%, 1.27 is 127% and so on.
Choose left or right button in the options. Easy to scroll to the perfect size for any page.
Nice add-on.

Wow! Wonderful little helper!

Especially the option to use the left mouse button too, because my right one is already taken for system-gestures.

I use it in combination with "Zoom Page WE"-Addon. I guess it takes the zoom-steps etc. from there. Perfect!

Great! Thank you very much!

PS: One little thing though: It would be better, if the highlighting of the text would be disabled while zooming. ... Maybe you can implement this? ... ;-)

Tested in Firefox 84. A simple yet effective extension that works as expected.

good but what about the zoom levels settings?

Works but you have to restart your browser after install, or it works only with new tabs.