tremere110: So, no way to map zoom to the keyboard. In order to play this game you need a physical mouse with middle wheel. The game loads saves fully zoomed so it becomes unplayable without that mouse. Hopefully the devs fix this soon. If you have a laptop I recommend avoiding this game until it's fixed.
What about scrolling from the trackpad? I've noticed on Macs, that has been the equivalent to a scrollwheel on a mouse.
On a Mac notebook scrolling with the trackpad is done by sliding two fingers on it. It's actually 360° scrolling, so for zooming I would try more of an upward/downward motion for out/in (or in/out) rather than leftward/rightward. Be sure to try both upwards and downwards because the zooming might not be intuitive.
Don't have the game yet, so I can't try it. Maybe it might work on your computer?