Has anyone found a solution to the OPs question? The reason you hold shift while zooming is to lock an object along an axis to move an object to another location and often zooming in and out is the quickest way to the other location.I am sure alot you do this without realizing. I used to do this all the time on a pc and i really miss it now on the mac. It seams like holding shift modifies the scroll direction to horizontal an a mac. It seems like a solution would be to make horizontal scrolling zoom in and out in sketchup but i am at loss as for how to go about that. Any ideas on how to get it working?