Tenn. Code § 13-7-102
From and after the time when the regional planning commission of any planning region defined and created by the [former] state planning office makes and certifies to the legislative body of any county located in whole or part in such region a zoning plan, including both the text of a zoning ordinance and the zoning maps, representing the recommendations of such planning commission for the regulation by districts or zones of the location, height and size of buildings and other structures, the percentage of lots that may be occupied, the sizes of yards, courts and other open spaces, the density and distribution of population, the location and uses of buildings and structures for trade, industry, residence, recreation or other purposes and the use of land for trade, industry, residence, recreation, agriculture, forestry, soil conservation, water supply conservation or other purposes, and identify areas where there are inadequate or nonexistent publicly or privately owned and maintained services and facilities when the planning commission has determined the services are necessary in order for development to occur, then the county legislative body may, by ordinance, exercise the powers granted in § 13-7-101 and, for the purpose of such exercise, may divide the territory of the county which lies within the region but outside of municipal corporations into districts of such number, shape or area as it may determine and within such districts may regulate the erection, construction, reconstruction, alteration and uses of buildings and structures and the uses of land. All such regulations shall be uniform for each class or kind of buildings throughout any such district, but the regulations in one (1) district may differ from those in other districts. The regional planning commission may make and certify a single plan for all the territory of the county which lies within the region but outside of municipal corporations, or may make and certify separate and successive plans for parts of such territory which it deems to be suitable for urban or nonurban development or which for other reasons it deems to be an appropriate territorial unit for a zone plan; and correspondingly, any ordinance enacted by the county legislative body may cover and include the whole territory of the county which lies within the region but outside of municipal corporations covered and included in any such single plan or in any such separate and successive plans. No ordinance covering more or less than the entire area covered by any such certified plan shall be enacted or put into effect until or unless it is first submitted to the regional planning commission and is approved by the commission or, if disapproved, shall receive the favorable vote of not less than two-thirds (2/3) of the entire membership of the county legislative body.
T.C.A. § 13-7-102