Before the technical issues you need to research the legal ones.
I'm not familiar with the details, but depending on your status in Germany and the length of the relocation, you may be able to keep the bike as US-registered, without officially importing it into Germany. I know US servicepeople stationed in Germany commonly do this, not sure about other cases.
I'm not sure if you're .mil, but this may be helpful:
https://installations.militaryonesource.mil/military-installation/usag-bavaria/transportation/motor-vehiclesWithout special status, foreign citizens can drive a foreign-registered vehicle in Germany up to 6 months (intended for tourists, and may not apply in other cases).
If it does need to be registered in Germany, it'll most likely need to be formally homologated in Germany, which may or may not need various HW/SW changes, depending on what the differences are between US & EU models (Zero would be the source for that info); also, the bike will likely need to pass the tough TÜV inspection.
It's also possible, if the homologation requires non-minor HW changes, that bringing the bike back to the US afterwards will require undoing the changes and re-homologating it for the US.
I also expect, that if the bike
isn't homologated & registered in Germany, selling it to a local citizen gets complicated, and requires both that person paying various import taxes on it, getting it homologated, and lots of extra paperwork.