Looking at your editor's update
method, your first call is to mouseWheelUp
, which resets the internally cached mouse wheel event value to 0. On your second call to mouseWheelDown
the value will be 0 and therefore the return result of that method is always false.
You should approach that problem differently. You could for example introduce some kind of mapping to a constant or enum that signifies a mouse wheel up or down event. Or you could process in your update method the raw incoming event value instead. That's probably the better way since it's apparently a delta value that may be more or less big depending on how much you spin the mouse wheel. You should take the delta into account for making bigger or smaller changes to your zoom value.