OverZip is an addon utility for ZIP and other archivers which compresses ZIP and other packed files even more using special compression algorithm. It can help more in the case of huge archives with many files. Since archive files are already compressed, the size reduction may be relatively small. But still, OverZip compression runs about as fast as the copying, so it is free, so to speak, and every little bit helps.

The license of this software is Free Trial Software, the price is $19.95, you can free download and get a free trial.