Complex sentence: His father, Zbigniew Szulc-Krzyzanowski, was an engineer from Poland who was a tank commander during the WWII in the Netherlands, where he stayed after the war and married Clotilde Laurijssen in 1946.
Split into simpler sentences: His father, Zbigniew Szulc-Krzyzanowski, was an engineer from Poland. During the Second World War he was a tank commander in The Netherlands, where he stayed and married Clotilde Laurijssen in 1946.