Edited KMZ/GPX segments don't show on map

I'm in awe with how convenient and easy it is to retrack my routes after the fact and I love the results I can share. However, while I've had great success in importing and editing the GPX files I used on my latest travel through France, I'm unable to efficiently convert the .KMZ files from my previous trips. Those are the only files I have from a 9-months journey. I used ExpertGPS to do the convertion but the segments I edited or added by hand in my Google Map don't appear on the .GPX when I import them to the Map.