how to search by postal code

as the plugin is supposed to be a geographic directory.

i was thinking location search would be very easy.

actually i have added some listings.

but i cannot figure out how to get good location results out os a map search.

postal code never found
town : ok in the same towns but near places are not listed by distance

district : 2 first number of the postal code is usually listing all the places with the same 2 first numbers.
not working neither.

i am a bit surprised about those geographical results.
i feel a text search on the postal code might be even more efficient