Shell scripting with zsh with unknown path

[TJ Luoma <luomat@gmail.com>]

I have always written my shell scripts in #!/bin/sh or 
#!/bin/bash but there are times when I find that I would really 
prefer to use zsh.

Ideally I'd like to be able to write all of my scripts in zsh so 
I don't have to keep two syntax/feature sets in my head.

The problem is that I don't always know where zsh will be 
installed. It could be /usr/bin/zsh or /usr/local/bin/zsh or /bin/zsh.

I have seen perl scripts which have used

     #!/usr/bin/env perl

but that did not seem to work for zsh.

TjL