Due to the cancellation of the Junior Grand Prix, van Zundert opened her season by making her senior international debut at the 2020 CS Nebelhorn Trophy, where she was the youngest competitor. She earned all personal bests to finish seventh overall. Her coach was unable to travel from Belgium and she was accompanied by Lorenzo Magri, an Italian coach she knew from training. After the competition, she announced she was leaving her longtime coach, Ans Bocklandt, to train under Jorik Hendrickx and Carine Herrygers in Eindhoven and Tilburg. In November, van Zundert won her first international title at the 2020 NRW Trophy, ahead of Josefin Taljegård and Jenni Saarinen. Her results earned her the technical minimums for the 2021 European Championships. Van Zundert competed at several other Senior Bs throughout the season, winning medals at the Winter Star (silver) and Celje Open (gold).