Thanks all for the help.

I don't know what I did wrong last time (maybe I installed a beta?).  I 
donwloaded the latest Ruby file, compiled it, and now I have what appears 
to be a functinal zlib:

$ ruby -e 'require "zlib" '
$

So it looks like the standard Ruby install comes with everything I'll 
need.  I'll see if I can use zlib directly so as to avoid asking the user 
to also install rubyzip.rb.

Or maybe I'll include a copy of rubyzip.rb with the package.

In any event.  I'm happy to have zlib.

Cheers,
-- 
Daniel Carrera    | OpenPGP KeyID: 9AF77A88
PhD grad student. | 
Mathematics Dept. | "To understand recursion, you must first
UMD, College Park | understand recursion".