Complex sentence: The stadtholder had been appointed by the sovereign (the Dukes of Burgundy or the Habsburgs) in each province as his representative, although traditionally Holland, Zeeland and Utrecht had the same Stadholder.
Split into simpler sentences: The stadtholder had been appointed by the sovereign (the Dukes of Burgundy or the Habsburgs) in each province as his representative. Traditionally Holland, Zeeland and Utrecht had the same Stadholder.