If I press the Tab key, it opens a window to shutdown, log off, etc. the computer. The Z key does "undo". The number one key reloads the page. The Esc key acts like Ctrl+Alt+Del. If I try to use any of the keys, it won't work unless I press it quickly multiple times. I don't have any sticky keys enabled under System → Preferences → Assistive Technologies.
Sounds like your CTRL key is stuck (CTRL+Z is normally undo). Try a different keyboard (if on a laptop, try an external one) to see if that works.
Also try cleaning your keyboard.