Sample script that searches Active Directory for all users with the Zip code 98052. The postalCode attribute is not replicated to the Global Catalog; you cannot connect to a Global Catalog server and search across the forest for users from a specified zip code. Note that this attribute is not automatically populated any time you create a user account.

Visual Basic
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On Error Resume Next

Const ADS_SCOPE_SUBTREE = 2

Set objConnection = CreateObject("ADODB.Connection")
Set objCommand =   CreateObject("ADODB.Command")
objConnection.Provider = "ADsDSOObject"
objConnection.Open "Active Directory Provider"
Set objCommand.ActiveConnection = objConnection

objCommand.Properties("Page Size") = 1000
objCommand.Properties("Searchscope") = ADS_SCOPE_SUBTREE 

objCommand.CommandText = _
    "SELECT Name FROM 'LDAP://dc=fabrikam,dc=com' WHERE objectCategory='user' " & _
        "AND postalCode='98052'"
Set objRecordSet = objCommand.Execute

objRecordSet.MoveFirst
Do Until objRecordSet.EOF
    Wscript.Echo objRecordSet.Fields("Name").Value
    objRecordSet.MoveNext
Loop