That's a lofty goal, and probably impossible with the improvements they are suggesting. Just reducing speed (increasing congestion) and installing more traffic lights/crosswalks won't eliminate all traffic deaths.
To actually accomplish something like that you would need to radically redesign the city. Eliminate non-autonomous cars, build a really first class subway system (bus accidents are a thing!), go all-in on elevated walkways, invent some kind of really effective suicide counseling, etc...
That said, even if they "fail" and only eliminate 90% of the traffic fatalities/major injuries that's still a big win IMHO.
I think speed reduction is the biggest. Yes, zero does sound almost impossible. US commercial air travel had zero deaths in 2017, so that should give some confidence.
Commercial air travel doesn't have to deal with pedestrians.
That's basically my option B from above. Ban all surface transportation and massively expand the subway system. Also redesign the subway system so it can deliver packages now. Absolutely no chance in hell of getting that done by 2025. Oh, and also redesign all subway platforms so people can't use them to commit suicide.
Or maybe they're trying the London option and making gridlock so bad that no car ever gets enough speed to seriously injure a pedestrian.
http://visionzero.lacity.org/
The goal isn't to minimize deaths per mile driven or per hour, it's to eliminate deaths period.