1.  In order to avail itself of the powers conferred by this chapter, the board of supervisors shall appoint a commission, a majority of whose members shall reside within the county but outside the corporate limits of any city, to be known as the county zoning commission, to recommend the boundaries of the various original districts and appropriate regulations and restrictions to be enforced therein. Such commission shall, with due diligence, prepare a preliminary report and hold public hearings thereon before submitting its final report; and the board of supervisors shall not hold its public hearings or take action until it has received the final report of such commission. After the adoption of such regulations, restrictions, and boundaries of districts, the zoning commission may, from time to time, recommend to the board of supervisors amendments, supplements, changes or modifications.

   2.  The zoning commission may recommend to the board of supervisors for adoption a comprehensive plan pursuant to section 335.5, or amendments thereto.

   3.  The zoning commission, with the approval of the board of supervisors, may contract with professional consultants, regional planning commissions, the economic development authority, or the federal government, for local planning assistance.