All unimproved or agricultural territory that may hereafter be annexed to the City shall be considered as lying in the AG Agricultural/Urban Reserve District until such classification shall be changed as provided by this ordinance. Any improved property that is annexed into the city shall be zoned according to the zoning district that most nearly describes either its present use or the use proposed by Denison’s Comprehensive Development Plan. This zoning shall be established by the Planning Commission and the City Council at the time of annexation.