Agreed Tony and Motornissen, this makes the most sense. Zero is not going to go to the 300v range any time soon if ever, and many CCS stations only work (for now) between 300 and 450 volts DC. Trouble is I think that would be over the max input voltage range of the chargers unless you combine 2 chargers in series on the input side, tell the station you want the full 450 volts and get 225 vdc as input per charger. Wow then you can also parallel chargers this way to get more amps out of the station.
For right now, you can source enough power using 2 J plugs to max the 1 C charge limit out of a Zero, or just 1 Tesla destination charger. In fact the Tesla destination charger is just a good to us as the CCS or CHAdeMO but there are 700% more of them out there. So if the 1C limit were ever to go to 2C you could still charge with 2 Tesla plugs, but then it might make sense to figure this out. For now using the DC charging network to try to charge a Zero doesn't make much sense when there are so many better options.
Again I wish the fast charging police would come in and force all the stations to go down to 50 volts, but because of the desire to reduce cost of the stations, making them only run 300-450 volts must have been a consideration and property owners have the ability to buy the lowest cost DC chargers which are probably not ones that go to 50 volts.
Because one day it would be nice to charge without having to carry the chargers onboard, but this past year with the Diginow superchargers now being so small, carrying 1C of charging on any Zero is not impossible anymore. And that's the best you could get anyway!