The planning director shall be responsible for the preparation of the zoning resolution and for submitting it to the county planning commission for its consideration and action. The commission shall review the proposed zoning resolution and, after holding at least one public hearing on each proposed action, shall approve or reject it in whole or in part and with or without modifications. When approved by the commission, the proposed resolution shall be submitted to the county board for its consideration, and the zoning resolution shall become effective when adopted by the county board. The county board of such county may amend, supplement, or otherwise modify the zoning resolution. Any such proposed amendment, supplement, or modification shall first be submitted to the planning commission for its recommendations and report. The planning commission shall hold at least one public hearing with relation thereto, before submitting its recommendations and report. After the recommendations and report of the planning commission have been filed, the county board shall, before enacting any proposed amendment, supplement, or modification, hold a public hearing in relation thereto. Notice of the time and place of hearings above referred to shall be given by publication thereof in a paper of general circulation in the county at least one time at least five days before the date of hearing. Notice with reference to proposed amendments, supplements, or modifications of the zoning resolution shall also be posted in a conspicuous place on or near the property upon which the action is pending. Such notice shall be easily visible from the street or highway, and shall be posted at least five days before the hearing.