Another alternative can be a parking lot near the gas station, outside the walls of Assisi, so again you would not have problems with ZTL.
The parking lot is small, so it will not always be possible to find park, but above all pay attention to the white stripes since some of the spaces are reserved for residents. Anyway it is prescribed by the road signs where you can park in peace.
There is also a charging station for electric cars with parking.
The Google Maps link to the parking is this -> Link