Any ordinance or resolution adopting any such plan or regulations, or any part thereof, may be amended, supplemented or modified by subsequent ordinance or resolution.

Proposed amendments, supplementations, or modifications shall first be heard by the commission and the decision shall be made and reported by the commission within ninety days of the time that the proposed amendments, supplementations, or modifications were made.

The council or board, pursuant to public hearing called by them upon application therefor by any interested party or upon their own order, may affirm, modify or disaffirm any decision of the commission.