Do you mean in the Zoom area of the scroll bar? There a lot of different ways to zoom in Logic - and I'm not sure which you're asking about.
Also, what version of Logic and OS X are you running?
You can assign key commands to the Zooming Functions.
Go to [b]Logic > Preferences > Key Commands[/b].
Then Navigate to [b]Various Windows[/b] and in there are the Zoom functions. To get there fast you can type Zoom in the search bar and it will bring up the Zoom functions.
I have used the Ctrl and the arrow keys to assign the Horizontal and Vertical Zoom. This makes for quick and easy zooming inside my Logic projects.
[url=http://www.macprovideo.com/forum/upload/upload/server/php/savedfiles/files/mpv_40089_14931_Zoom_Commands.png] [img]http://www.macprovideo.com/forum/upload/upload/server/php/savedfiles/thumbnails/mpv_40089_14931_Zoom_Commands.png[/img] [/url]