Hello!
You can search by anything including ZIP codes in the location field. If you have a directory for one country only, that should work well. For a worldwide directory, the system might interpret ZIP codes as belonging to more than one country, and will make a choice, which might be now what the visitor had in mind.
Have a look here:
https://wpgeodirectory.com/docs/core-design/#how
https://wpgeodirectory.com/docs/core-general/#search
There are some shortcodes available for the Multilocations plugin that might be worth looking at to create a list of popular locations:
https://wpgeodirectory.com/docs/location-manager-shortcodes/
For highlighting listings we recommend you use the “Featured” property of the listing package, part of the Payment and Package Manager addon:
https://wpgeodirectory.com/docs/prices-and-payments-add-on-overview/
Featured can put a custom graphic, and allow you to set your sort to return featured listings first.
“Featured” is available as property for several core shortcodes, too:
https://wpgeodirectory.com/docs/core-shortcodes/