Zoning to prohibit people from living on 99% of the land so that the population is dense enough to fully benefit from public transit? Lots of states don’t even have a true city at all. Should those be zoned as national parks?

Edit: I think I missed the point. You’re talking about just city zoning. Still, not a magical fix and would likely require moving lots of people and demolishing/building buildings and infrastructure. However, it’s more realistic than zoming everyone out of the midwest.