If you are syncing Zwift to your Garmin account, and tracking your Zwift ride with watch, it is probably pulling in from both places.
My zwift rides upload to Garmin, and I track with my computer as well, just incase something crashes. I always end up with two of the same rides/workouts in Garmin & TrainingPeaks so I’ve gotten into the habit of deleting one after each workout. I would guess Optimize is doing the same, importing both files of the same ride.
That sounds like what I did.
Trying to figure out what the recipe is to get just one ride logged….
First try: unsync’ing my Garmin from the Zwift Connections page.
This should allow outside rides (Garmin Edge or Fenix) to go to Optimize. But, my Garmins push to TP. So, I wonder if Optimize will take the ride from the Garmin device and then, also, take the same ride from TP after the Garmin pushed the ride over to it🤷♂️.