Look at Houston, all sprawl, there will never be a chance for real mass transit there. Not to mention a host of other issues. Lack of zoning also means complete and utter lack of planning, developers build whatever gets them the biggest buck today, who cares if it makes any sense for anyone else.
Cities should be planned, and zoning should support that plan. Obviously there are issues with zoning as protectionism, but lack of zoning doesn't lead to better results. Since you claim it does, link of some studies that show reduced zoning results in better outcomes for cities.
Also just because places have zoning doesn't mean it's actually restrictive. OKC has zoning, but it's trivially easy to get it changed.