Google Earth allows users to store routes and other map data into a single compressed file, using the KMZ (Keyhole Markup Zip) format. But if you want to use those same routes and waypoints packaged in your KMZ file on a Garmin GPS system, you'll first need to convert your KMZs into a Garmin-compatible format. With the help of some free utilties, you can convert your KMZ files into GPX (GPS exchange) format and import your saved map data to your Garmin device.
Go to the GPSies conversion web page (see Resources). Click on the utility's "Browse" button to upload the KMZ file from your computer into the converter.
Select either the "Track" or "Waypoint" option to convert your KMZ file into a GPX route or waypoint. Select the "GPX" option from the drop-down menu located next to the option you choose.
Click on the "Convert" button to begin the conversion process.
Open POI Manager on GPS Data Team's website (see Resources).
Click on the "Browse" button under the "POI Manager" heading to import your KMZ file into the utility. Click "Open."
Click on the "GPX" option on the next page to save your KMZ file as a GPX.
Download a free copy of KML/KMZ to GPX Converter Freeware (see Resources). Start the program after installing it.
Click on the "Import KML/KMZ" button at the top of the program and import your KMZ file into the program.
Click on the "Export GPX" button to save your KMZ file in GPX format.