I've tried uploading my logs to PhantomHelp's DJI Flight Log Viewer and downloaded the KMZ file.  However when I play the tour in Google Earth, the length and speed appears to be incorrect.

For example, a ~12 minute flight shows as ~36 minutes and when playing back jumps between waypoints/markers.

Is there a way to easily create a KMZ that plays the flight correctly in Google Earth? I have seen some guides that extract the subtitles from the video, but the tools I have used only appear to support MKV files.

Have you tried the airdata export, they are partnered with DJI to have proper access to the log.