Finger slip - all tracks minimized except the one I'm working on

This has happened a few times. I reach for ctrl-Z to undo, my finger slips and I hit something that causes all the tracks to vertically minimize except the one I’m working on, which gets greatly enlarged. This can actually be useful, so does anyone know what I’m accidentally hitting? I’ve looked around the menus but couldn’t find anything relevant. Also, when I do this by accident, is there a way to undo it?

–Neil

Sounds like Z is assigned to Zoom Tracks exclusive.