Houston doesn't have zoning, but it has development regulations that include many of the same restrictions found in the zoning codes of other US cities.
From the webpage: "The City codes do not address land use."
These regulations appear to deal with things like setbacks, street access, etc. but it sounds like you can do whatever you want on the land. I think these regulations are just to deal with how to divide up a parcel of land, rather than to regulate anything you do with it.
And, independent of local zoning, our financial system drives hard for the type of stuff that zoning also reinforces. When easy capital supports single family houses and large projects, everything in between is crowded out.
That was the point I was trying to make above. Zoning is more a reflection of what is most profitable for developers, so you get similar results in cities with zoning and without.
https://www.houstontx.gov/planning/DevelopRegs/