All territory hereafter annexed to the City of Blue Mound, Texas, shall be classified as “B” Residential District, until permanently zoned by the City Council of the City of Blue Mound. The City Planning and Zoning Commission shall, as soon as practicable after annexation of any territory to the City of Blue Mound, institute proceeding[s] on its own motion to give the newly annexed territory a permanent zoning, and the procedure to be followed shall be the same as is provided by law for the adoption of original zoning regulations.