How to define sub level for zones in opencart 2.3.0.2

Currently open cart only support for country and zones. How can I define sub level for zones
Example: Country, Zones and city => Country: US, Zones: California, City: San Diego, San Francisco, Los Angeles, etc.

By default, Opencart stores do not contain any cities either. However, you can look up for an extension on the marketplace as many different versions of them can already provide the solution that you need.