I‘m considering a small led just at the back of where the high level brake light is on the ZS. It would be a nice neat fit and take power straight off the supply to the led brake light. You could then see the small red light when the brake lights were on from your rear view mirror.
(My Model3 shows all lights that are on, on a schematic of the car - including brake lights, indicators, headlights etc which has spoilt me a bit).
I’m not too fussed about this when using the friction brakes as I’m pretty sure the brake lights illuminate then. It’s the regen brake lights that it would be good to see as I’m not too sure that these give much warning to other road users - I tend to get quite a lot of drivers who rely on brake lights, backing up to me when I slow under regen only.