Welcome David to our group and thanks for your post.
I have not used zimmermann myself and when searched for it on the
Webheads in Action I did not find any references to it.

But you have reminded me about a presentation I attended at the
GLoCALL conference in Hanoi in November - I think it was a software
only available on Macs - I will double check my notes.

Do you have any URL to the Zimmermann software? Sounds very promising

R