AdvanceCOMP is a collection of recompression utilities for your

  .ZIP archives
  .PNG snapshots
  .MNG video clips
  .GZ files

The main features are:

  * Recompress ZIP, GZ, PNG and MNG files using the Deflate 7-Zip
    implementation
  * Recompress MNG files using Delta and Move optimization

WWW: http://advancemame.sourceforge.net/comp-readme.html