I don’t like many of the definitions of zonig I have seen, some capture the legal meaning, some the regulatory and some the act of planning, but not all three. Some cover land use, some development. So I will have a go based on one of the Cambridge English Dictionary definitions but more specific.
Zoning
The act of setting rules in a regulatory ordinance affecting real property for the use and/or the design of development that can or cannot be built on geographically specified areas of land.