Slow Unzipping or Errors Unzipping (Depreciated after version 0.50.0) - MegaMek/megamek GitHub Wiki

Please note the following applies to release in the 0.49.x Release cycle and earlier.

See here - for specifics for releases starting with 0.50.0-Development

Don't use Windows' built-in zipper. It is known to have issues unzipping programs with large number of files, and is regularly the cause of inexplicable and hard to track down issues.

We recommend 7-Zip, an open source free zip program. 7-zip is significant faster, significantly more stable, and handles more file types than the base Windows zipper. However, other zippers (other than the broken Windows zipper, that is) should work as intended.