Custom Keyboard Shortcut for Shutdown Command

[gollum17]

Hi everyone I have been working on trying to get a keyboard shortcut to work for the shutdown command for convenience mostly.
Is it possible?

I have already gave myself su rights to the shutdown command, so I know its not an access/account problem.

This is what my shortcut looks like in the custom shortcuts menu of keyboard.

Name: Off (Simple enough)
Command: Shutdown -P now
Shortcut: ctrl+z

Obviously there is something wrong with my command, does anyone have any suggestions/help for me.