The division of a city by legislative regulation into districts and the prescription and application in each district of regulations having to do with structural and a7chitectural designs of buildings and of regulations prescribing use to
which buildings within designated districts may be put. Miller v. Board of Public Works of City of Los Angeles, 195 Cal. 477, 234 P. 381, 384, 38 A. L.R. 1479; Elizabeth City v. Aydlett, 201 N.C. 602, 161 S.E. 78, 79.