Except for programs that support KML to KMZ conversion, you can simply pack your .kml files with any ZIP supporting programs as .zip archive and rename ZIP to KMZ. This should work simply because a .kmz file is just a zipped version of .kml file for the purposes of reducing file size.
Convert Google Earth Keyhole Markup language file to Compressed Keyhole Markup Language (Google Earth) data.
We have found 4 software records in our database eligible for .kml to .kmz file format conversion.
Microsoft Windows software - convert kml to kmz on Windows
MAPC2MAPC is a Windows program to manipulate digital maps and convert them between different platforms and software.
Convert from kml file
to kmz file
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned kml to kmz. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
MyGeodata Cloud can be used to convert and transform both vector and raster geospatial data to various formats - online and for free.
OkMap is a free software for many outdoor activities that might require a map. It can manipulate maps, trade data with mapping services, and more
RoboGEO is a program that allows users to geocode their photographs and pictures. Used by thousands of companies and governments worldwide, RoboGEO is the best-of-breed solution for geocoding digital photos.