is where the images are that you would replace with the Zenyth key PNGs.
Using a file explorer with capabilities to extract and zip, like Root Explorer;
*Copy the PNGs to location listed above under the extracted file, accepting the replacement of the necessary files (multi select and move all at once for convenience)
*Create zip of SystemUI and rename from SystemUI.zip
and move to and replace under /system/app
*Phone should reboot and you should be good
**Permissions are XX-XX-X-- if you need to alter them, but you shouldn't
Create a backup, just in case, and maybe keep a renamed copy of SystemUI if you want to easily revert. Can be done on the phone in a matter of minutes. Very simple!
I can't imagine this being any different under 4.2.2 and if you need further explanation just ask.