Tenn. Code Ann. § 7-21-407

The creation and establishment of a unified government under this chapter shall not alter or change zoning regulations effective in the county and in the unified municipalities, but the zoning regulations shall continue until modified or changed by the legislative branch of the unified government acting under authority of its charter. The creation and establishment of a unified government under this chapter shall not alter or change zoning regulations effective in a smaller city that has not elected to merge with the unified government, but the zoning regulations shall continue until modified or changed by the legislative branch of the smaller city or until the smaller city shall elect to become a part of the unified government pursuant to § 7-21-107.