I change regularly browser for various reasons. After being returned to Firefox, I discovered that the « pinch to zoom » feature of my MacBook wasn’t working.
Then I tried to find why on the web and I found this article. The solution was simple but I didn’t like the idea to modify those settings for each installation of OS X or Firefox.
So I implemented an add-on for Firefox that modifies those settings. The behaviour is not as fluid as in Safari but it works.