Complex sentence: De âlde Friezen (The Old Frisians) is the anthem of Frisia as a whole and also that of West Frisia, the Frisian province of the Netherlands.
Split into simpler sentences: De âlde Friezen (The Old Frisians) is the Frisian national anthem. It is also the official anthem of West Frisia, the part of Frisia governed as a province of the Netherlands.