Well, to a Mac colleague of mine, I was boasting off a trick that I learnt recently from – Minimising windows in OS X. But I was defeated at my own trick when he did something – zoom in and out on his screen.
Here is the trick – Hold the Ctrl key while scrolling with two fingers. If you do not know how to scroll with two fingers, you better learn that (it is a real productivity booster). The TouchPad of a Macbook allows you to tip on with one finger and scroll with the another finger. It did took me some practice to get use to using two fingers on the touchpad/trackpad.
Do some practice and you should be able to zoom in and out. Enjoy!