Keyboard Shortcut Conflicts

Is there a way to override Premiere Pro shortcuts when your custom CEP Panel is in focus? For instance, I'm trying to get the Cmd+Z and Cmd+Shift+Z shortcut for a text field in my panel, but it keeps triggering the Premiere Pro undo command instead.

  $("#editor").on("keyup", function(e){       e.preventDefault();       if(e.keyCode == 91 && e.keyCode == 90)       {       undoEdit();       }  });

I know the code works since I tested it with each key individually, and I believe e.preventDefault() is supposed to allow this, but it's not working in my case. Any thoughts are appreciated. Thanks!