PBEM Overlays App
This great little App from Mark Ainsworth lets uou create overlays such as rulers, range-sticks, protractors, etc. that you can have sit o top of your Vassal or Cyberboard game. I suspect it will work fine with ZunTzu too.
The App comes with text files explaining how to use it. Follow these and you'll quickly be able to create and use an overlay of your choosing.