Said zoning plan consists of the establishment of various districts within the unincorporated territory of said county within some, all or none of which it shall be lawful, and within some, all or none of which it shall be unlawful to erect, construct, alter or maintain certain buildings or to carry on certain trades or occupations or to conduct certain uses of land or of buildings; within which the height and bulk of future buildings shall be lim-ited; within which certain open spaces shall be required about future buildings and consisting further, of appropriate regulations to be enforced in such districts, all as set forth in this title.