In January 2019, Zehnder's coach Cornelia Leroy presented both her and her now partner, Beda Leon Sieber, with the opportunity to compete as a dance team at the 2020 Winter Youth Olympics, a home event for the Swiss teenagers, and together, they chose to switch disciplines with that goal in mind.

Despite being newcomers to ice dance with less than a year of training together under their belts, Zehnder and Sieber won the national title by an over nine-point margin over silver medalists Alina Klein and Maxim Kobelt, and were named to the Swiss Youth Olympic team.

At the Youth Olympics in January, then-14-year-old Zehnder had the honor of lighting the cauldron at the event's opening ceremony as the youngest athlete in the Swiss delegation.

Zehnder and Sieber concluded their debut season at the 2020 World Junior Championships where they placed 29th in the rhythm dance and did not advance to the final segment of competition.

Zehnder and Sieber competed at one final event in the fall in the lead up to their national championships, the 2021 Autumn Talents Cup, where they claimed their first international medal, a silver behind Ukrainian team Myroslava Tkachenko and Andrii Kapran In November, Zehnder and Sieber defended their junior national title at the 2021 Swiss Figure Skating Championships, winning gold again by an approximately nine-point margin, this time over compatriots Kayleigh Maksymec and Maxmilien Rahier.

The team's only other event during the season was the 2022 Swiss Figure Skating Championships where they placed second in the junior dance category behind Milla O'Brien and Laurin Wiederkehr.