If any software can be used to work with or convert .gmz files to .gmk files, it would be GameMaker from which both of these files originate. Based on the file types, gmz to gmk conversion is probably related to import of source to the projects. In any case, if you have trouble with import of .gmz files or export of .gmk files, it would be best to contact GameMaker community forums or support.
Updated: February 9, 2023