Although somewhat uncommon, some 3D objects can sometimes saved in KMZ format (Compressed Keyhole Markup Language) which makes it difficult to open in some 3D modeling programs. This makes some user look for a conversion to a different format, in this case 3D object. Such kmz to obj conversion can be for example done using programs like Blender or similar.
Open KMZ file Open OBJ fileA CAD 3D geometry translation software