Nothing in this chapter shall be construed to remove or limit the powers of the cooperating cities, counties, school districts, benefited water districts, benefited fire districts, sanitary districts, or similar districts as provided by state law. All legislative power with respect to zoning and other planning legislation shall remain with the governing body of the cooperative cities and counties. Each participating city or county may continue to have its own planning commission or board but may, under the joint agreement and in the interest of economy and efficiency and in the interest of uniform standards and procedures, request the metropolitan or regional planning commission to assume duties and functions of local planning agencies in whole or in part. The metropolitan or regional planning commission shall have the duty and function of promoting public interest and understanding of the economic and social necessity for long-term coordinated planning for the metropolitan or regional area, but its official recommendations shall be made to the governing bodies of the cooperating cities, counties, school districts, benefited water districts, benefited fire districts, sanitary districts, or similar districts.