Thank you for filling out the report! We have tried reproducing the issue but so far we haven't been able to. However, upon looking up for potential scrolling issues with firefox there are some reports of that with version 35.0.1 - particularly in combination with add-ons. You may try disabling the add-ons if you have any and see if that makes a difference.
There's also a 36.0 version for Firefox, updating may resolve the issue. But that version includes new features/warnings and whatnot, so try that as a last resort as you may not like the update.
I did the update to 36.0 and the problem is still the same.
Edit: I notice that, if i switch from a different browser, open window, open word/excel file etc, the problem with zoom in zoom out exist. But, if i click once on the game area (outside my city borders or inside for example on a building) i can do zoom in out normally.
Update: I disable all my Firefox add-ons and was totally fine. I tryed to enable one by one the addons so i can figure out the problem.
I notice problem with: WebTV PC Plugin NPDLL 3.0.2.33, Photo Gallery 16.4.3528.331 , Google Update 1.3.26.9. The bigger problem was with WebTV PC Plugin NPDLL 3.0.2.33 (this is a addon for a Greek cable tv)
Thank you for the update. Sorry for the trouble but glad we located the source of the issue!
I'm not sure if this can be fixed as it may be a conflict with the add-ons that cannot be resolved from Inno's side, but I will check and see if something can be done.
Apologies for any inconvenience but unfortunately this cannot be fixed since the issue is not from the game's side. You can try private browsing if you do not want to disable the add-ons, as most add-ons do not work in private browsing.