Where a city planning commission and a zoning board of appeals in a city of the metropolitan class already exist, their continuance is hereby authorized without further act of the city council. All ordinances, rules and regulations, hearings, orders, or decisions existing or in effect on April 1, 1925, or substituted or in effect thereafter, shall continue in effect, except insofar as any such ordinances, rules and regulations, hearings, orders, or decisions shall be in conflict with the provisions of sections 14-401 to 14-418.