The regulations, restrictions and boundaries set forth in this ordinance may from time to time be amended, supplemented, changed or repealed. Provided, however, any proposal to amend, supplement, change or repeal this ordinance shall first be made to the planning and zoning commission which, after considering the same, upon the affirmative vote of a majority of those present and voting at a meeting thereof may make a preliminary report thereon, conduct a public hearing with respect thereto and, at the conclusion of such public hearing, make a final report to the city council recommending the acceptance or rejection of such proposal. Provided, however, if the proposal to amend, supplement, change, or repeal this ordinance is referred to the planning and zoning commission by the affirmative vote of the majority of the members of the city council present and voting at any meeting thereof, then the planning and zoning commission shall be obligated not only to consider the same but to make a preliminary report thereon, conduct a public hearing with respect thereto and, at the conclusion of such public hearing make a final report to the city council recommending the acceptance or the rejection of such proposal. At least 15 days' notice of the time and place of the public hearing hereinabove provided for shall be published in a newspaper of general circulation in the city. When any proposal constitutes a proposed change in classification, written notice of such public hearing shall be sent to the owner of all real property lying within 200 feet of the property on which the change in classification is proposed, such notice to be given, not less than ten days before the date set for hearing, to all such owners who have rendered their said property for city taxes as the ownership appears on the last approved city tax roll. Such notice may be served by depositing the same, properly addressed and postage paid, in the city post office. Where property lying within 200 feet of the property proposed to be changed is located in territory which was annexed to the city after the final date for making the renditions which are included on the last approved city tax roll, notice to such owner shall be given by publication in the manner provided above.

If the final report of the planning and zoning commission recommends any amendment, supplement, change or appeal of this ordinance, the city council shall conduct a public hearing thereon and accept or reject such proposed amendment, supplement, change or repeal. Provided, however, if the final report of the planning and zoning commission rejects such proposal, then the city council need not call a public hearing and vote to accept or reject such proposal except on the affirmative vote of a majority of the members of the city council present and voting at the meeting thereof at which such final report is received. At least 15 days notice of the time and place of any such public hearing shall be published in a newspaper of general circulation in the city. In case, however, of a written protest against any change, signed by the owners of 20 percent or more either of the area of the lots or land included in such proposed change, or of the lots or land immediately adjoining the same and extending 200 feet therefrom, any amendment shall not become effective except by the favorable vote of three-fourths of all of the members of the city council.

Whenever it is made known to the city council that the planning and zoning commission has scheduled a public hearing required by the provisions of subsection 1 of this section [section 13.1] with respect to any proposed amendment, supplement, change or repeal of this ordinance, the city council may by resolution adopted by a majority of the members of the city council present and voting at any regular or any special meeting of the city council direct that the public hearing required to be held by the city council under the provisions of section 13.2 of this article with respect to such proposal being held jointly with such public hearing required by section 13.1 of this article to be held by the planning and zoning commission, but no action shall be taken on any such proposal by the city council until it has received the final report of the planning and zoning commission. Where such a resolution is adopted, a joint notice of such jointly held public hearing shall be published in a newspaper of general circulation in the city, stating the time and place of such joint public hearing, which time shall not be less than 15 days from the date of publication. Provided, however, where such a resolution is adopted, the notice to property owners required by section 13.1 of this article shall include a statement that the public hearing of the planning and zoning commission and the public hearing of the city council on such proposal shall be held jointly.