The manual says the BMS will prevent operation if the main pack is below -22°F. It says it’s not recommended to ride below 23°F, and if it is ridden that cold, to put it on the charger above 32°F as soon as the ride is over. It also mentions that in “extreme” cold, the power and range may be reduced. All those add up to operational, though not optimal/recommended, and all referring to the main pack (I think). It talks about the bike being disabled until the 12V pack heater can warm that pack to 32°F, but apparently the heater doesn’t keep it warm during the ride.
If Zero can't do anything for you suggest you install some type of heater for the 12v battery https://www.google.com/search?q=silicone+heater&client=safari&hl=en-us&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjo_5PR3oHnAhWWvp4KHX-_AwAQ_AUoAnoECA4QAg&biw=1024&bih=672
The main problem is that it takes quite a bit of electricity to heat up that much surface area enough to help much when it's cold. Also increases weight and expense.
Best to use ICE when it is that cold. Ice is used to the cold.
Maybe someday somebody will invent a battery that works well in the cold. That would be the best answer for a motorcycle. Electric cars have more room and battery KWHs to paly with than do motorcycles, and heating batteries is not a perfect solution even with the cars that use battery heaters.
-Don- Reno, NV