Areas annexed to the city shall be classified in the same or nearest comparable zone classification in which such area was classified in the county at the time of annexation until the council adopts different zone classifications in the manner provided for zone changes in Chapter 18.52 of this code. An area annexed to the city, which area was unclassified in the county at the time of annexation, may be classified in any zone classification by a temporary interim zoning ordinance adopted by the council until the council adopts different zone classifications in the manner provided for zone changes in Chapter 18.52 of this code. Zone changes may be initiated prior to the effective date of the annexation and may be effective upon the annexation. (Prior code § 10-3.501)