user: I'm working on a real estate project that requires me to analyze various properties in different cities, and I need to match the zip codes '90210', '10001', '60601', and '94102' with their respective cities for my market analysis. This information will be crucial for my next meeting with the investors. Could you help me find the cities for these zip codes?

Available functions:
name: retrieve_city_based_on_zipcode
description: Finds the city of a zipcode.
parameters: type: dict
properties: zipcode: type: string
description: The zipcode of the city.
required: zipcode