For some months Diederik is training a real talented dressage horse, called Bonzanjo, a top sport horse. His first important success was the first place in the Freestyle to Music at the National Championships 2013 (4th level 2nd test). Iin January 2014 he scored 72% in the international Prix St. Georges. His debut in the Grand Prix was in Hagen, Germany in March 2015. His first Grand Prix score was score there 75.450%. After March 2015 Bonzanje scored on average 75% in international GP competitions (Hagen and Stuttgart, Germany, London and Rotterdam, Maastricht and ‘s-Hertogenbosch, the Netherlands). His best score and personal record is 76.625 (Jumping Indoor Maastricht, October, 31, 2015).