Complex sentence: Its lack of connection has led to Jungholz being included in the German customs area, and its having both German and Austrian postcodes (D-87491 and A- 6691, respectively).
Split into simpler sentences: Its lack of connection has led to Jungholz being included in the German customs area. Letters to Jungholz can be addressed with German or with Austrian postcode (D-87491 and A- 6691, respectively).