John @Drumsagard -
With the Mavic 2 Pro/Zoom you need to reset it using DJI Assistant 2. Once in Assistant 2 - select the Mavic 2 and then select Firmware Update. You should then see the Factory Reset option - select and then select confirm. After all is done select Complete. This method removes all your data and links with the drone.
If you do not do Factory Reset then all the flight times etc that the new owner puts on the drone will be added to your DJI account as it will still be linked to your account- it won’t stop them from using it though. Having said that, it doesn’t mean that DJI won’t introduce some kind of restriction that could cause problems to the new owner at some later date 
Personally - I’d/will reset my M2Z when I sell it - just for peace of mind 