I own the mavic 2 pro and might be geting the zoom aswell.
I know they have the same batteries , but does someone know when you  interchange the batteries between  the drones if you dont have to keep updating the battery firmware on and on , or just once per drone and rc , so you do not keep getting firmware consistency.

Hi there, thank you for reaching out, we really appreciate you being interested with the DJI Products. With regards to that. No need to do that since both Aircraft is identical it just that the camera for each aircraft is different. Best Regards!

No, you don t have; You only need to update battery firmware when you update drone firmware. Since i bought both, every new firmware use to be released for both drones, at the same time.  Peace of cake.

,,, and after you update each firmware drone, you need to update the battery firmware once, on 2 pro or  zoom. And then you can use it free,