All territory within the City shall be classified as a part of that zoning district recommended by the Planning Commission and adopted by the City Council in accordance with the General Plan. All territory shall retain its classification unless and until it is otherwise zoned in the manner prescribed by law. The City may pre-zone unincorporated territory within the General Plan area of the City for the purpose of determining the zoning that will apply to such territory in the event of subsequent annexation to the City. The procedure for such pre-zoning shall be as prescribed in § 36-23 of this chapter, and such pre-zoning shall become effective upon annexation of the territory to the City.