Contacts Filter

Contacts Filter

I am building a Contacts app that contains;
Postal Code, State,County,City.
My requirement is to filter down with updating all the forms as I input or lookup. I am structuring as;
Postal Code (form)
>State (List Field)(Form)
>Zone(form)
>County(form)
>City(form
I have tried many ways to Bi Directional with Filters, but find doing double work at times. I am trying to determine the best way to handle 4 forms and filters at once.

Postal Code (input field)
State (Lookup Filter)

County (input field)
Zone(Lookup Filter)
State(Lookup Filter)

City(input field)
County(Lookup filter)
Zone(Lookup filter)
State(Lookup Filter)
Postal Code(Lookup Filter)

I am trying to make this fool proof as I can. Am I in the best direction? Also note that in some cases, I can not have "No Duplicates checked"

Can anyone point me in correct direction with theory?