Globally changing Redo to Ctrl-Shift-Z

Solution 1:

For the specific case of Word, File > Options > Customize Ribbon and hit the Customize button for keyboard shortcuts, then choose "All Commands", "EditRedoOrRepeat" and assign Ctrl+Shift+Z to it.

Solution 2:

It takes a little bit of extra work, but this is pretty much what AutoHotKey was designed for. You write scripts which capture keyboard combinations and then respond with different keyboard combos.

You would download the program, then right click on the desktop and choose "New > AutoHotKey Script".

The following script triggers Ctrl-Y when you type Ctrl+Shift+Z:

#NoEnv  ; Recommended for performance and compatibility with future AutoHotkey releases.
; #Warn  ; Enable warnings to assist with detecting common errors.
SendMode Input  ; Recommended for new scripts due to its superior speed and reliability.
SetWorkingDir %A_ScriptDir%  ; Ensures a consistent starting directory.

$^+z::Send ^y

Double click on the script to run & activate the swap.