bzip/zlib question

I have been looking through the documentation for using Bzip2 or zlib compression and have a couple of questions for the group... 1. Which is best to use on terms of: resultant file size, availability of decompression clients & ease of use? 2. Both bzip & zlib documentation makes use of *write() functions to add strings to the file, but can this be used to add files? 3. I intend to add two or more zip files to the archive so that the client only needs to download one file rather than several- which is most suited to this - zlib or bzip2? Mikey