About .ZIP File Format
To do word count in ZIP archives, let’s get to know a little more about this format. The ZIP file format is the most widely-used compressed file format in the IBM PC world.
The format was designed by Phil Katz for PKZIP, and in the form now used (PKZIP 2 format) it uses his DEFLATE algorithm for compression.
Today
Today, ZIP files use the file extension “.zip” and have the MIME media type application/zip. A ZIP file contains one or more files that are compressed or stored.
Many software utilities other than PKZIP itself are now available to create, modify or open zip files, notably WinZip, PicoZip, Info-ZIP, WinRAR and 7-Zip.
Link:
WinZip Home Page
7-Zip Home Page
WinRAR Home Page