You can create buttons with scripts that set the zoom level to a specific % or just zoom in and zoom out.
The zoom is still there. They just change what they look like. Click the plus and minus controls in the lower left corner of the window and you can still zoom your window in and out.
The one exception to this is if the layout was created with FileMaker 13's touch screen option in the new layout wizard and then an added trigger controlled script may have locked the zoom for your layout.
There it is! Thanks so much.
I'm still unhappy not to be able to use a keyboard shortcut, Marc. The script solution can't help me, because this is a company-wide database and custom scripts have been disabled. But up until now, custom keyboard shortcuts via Mac OS have worked.