Zenner qualified for two swimming events, as Germany's youngest swimmer (aged 17), at the 2008 Summer Olympics in Beijing, by storming victories in the 100 and 200 m backstroke from the Olympic trials, in FINA A-standard entry times of 1:01.24 and 2:12.61.[4][5] In the 100 m backstroke, Zenner challenged seven other swimmers on the sixth heat, including heavy favorites Reiko Nakamura of Japan and Laure Manaudou of France. She rounded out the field to last place and forty-second overall by one second behind Ukraine's Iryna Amshennikova in 1:03.87.[6] In her second event, 200 m backstroke, Zenner finished thirty-fourth overall in the preliminary heats with a slowest time of 2:20.28.[7]