For a sucessful kmz to kml conversion you have to use utilities like the MAPC2MAPC converter which allows users to transform map data to various formats. The program can be used to convert Google Compressed Keyhole file (.kmz) to Google Earth Keyhole file format (.kml).
You can also just rename kmz to zip and extract the content. Then import the .kml file to Google Maps. Just be mindful of the 3 MB upload size, it won't work with larger files.Open KMZ file Open KML file
A digital map conversion software
An online GIS converter
A GPS software for outdoor activities
A software used to geocode pictures