Complex sentence: It was the principal residence (winter residence) of the Hohenzollern Kings of Prussia from 1701 to 1918 (the German Emperors from 1871 to 1918) and a museum following the fall of the German Empire in 1918.
Split into simpler sentences: It was the principal residence and winter residence of the Hohenzollern Kings of Prussia from 1701 to 1918. It became a museum following the fall of the German Empire in 1918.