I am going to describe “enabling zooming in mac os x lion” step by step in this post.
Step 1 ) Click on System Preferences or Open System Preferences.
Step 2 ) Click on Universal Access.
Step 3 ) Select ON option under Zoom ( as illustrated in image below )
Step 4 ) Click on options button ( as illustrated in image above )
Step 5 ) Set the key to bind with your mouse wheel to zoom. The users used to with SnowLeopard zooming, would surely bind it with Ctrl Key. It is recommended/highly preferable to bind zooming with Ctrl key. Following image will illustrate where to bind it.