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. Said territory shall retain such classifications unless said territory is otherwise zoned in the manner prescribed by law. The city may prezone unincorporated territory adjoining 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 prezoning shall be as prescribed in Article 29 of this chapter, and such prezoning shall become effective upon annexation of the territory to the city. (Amended during the March 2009 supplement.)