I had a major problem with this:
This article solved the problem:
To save you time Here’s the solution:
1 – Go to System Preferences.
2 – Click on Universal Access.
3 – Click on Seeing Tab.
4 – Inside Zoom section, Click on Options.
5 – Check the checkbox at the bottom that says: Use scroll wheel modifier to zoom ^
Thats it. You should now have your screen zoom by holding Control + two finger slide up/down.
Here are some screen shots for further help: