Mysterious accidental shortcut messes up my project window

I hit it almost every day at least once. Annoys the bejesus out of me, always happens when I’m in a rush to do something quick… I don’t know what this function is, some kind of single track zoom? I have to manually zoom out and then resize the automation track. What am I hitting (I need to reassign this shortcut, it’s killing me!) and how to undo it?

Thanks

I hit something and this happens…

Z

Thank you. Got rid of it. Terrible default key assignment, kept hitting it when trying to use shift/alt/ctrl.