It's important to keep 'use scroll wheel with modifier keys to zoom' checked with a shortcut - i use Control. button lets you set the Zoom window size and some other stuff. once you check the 'Zoom in window' check box, the Options. Control-Option brings up the Zoom window only while you hold down those modifier keys. under Zoom, just click the box that says 'Zoom in window.' Option-Command-8 brings it up and makes it go away. I'm not sure how far back the info i am about to give goes, but on Lion in system prefs/universal access/seeing/zoom/ there is a preference you can set that is very much like Zoom It.
