For a 2014+ Zero, I believe the Eco mode you're presented with is the Custom mode you're allowed to modify. The app was designed for the 2013 model which let you customize Eco mode and, to some extent (regen settings), the Sport mode.
You can get access to the firmware for the motorcycle, using the OBD-II port above the motor (it's a capped port next to the fast-charging inlet). Hollywood Electrics sells
DigiNow's dongle for exposing this interface over bluetooth. It's a serial terminal application but does the job.
As someone who's developed mobile applications, I feel like community participation could clarify and brush up the app a bit, but it's difficult to breach NDAs (their protocol is proprietary and I'm sure there are security concerns) without them deciding to spend money on improving the app in the first place.
