A pair of American stars crashed out of downhill ski races on Saturday.
Vonn was second after the opening run. Vonn, a favorite in the upcoming Vancouver Olymics, kept her lead in the overall standings.
"I have been fighting really hard. I had a mistake early on," Vonn said. "The light wasn't too good anymore. I gave everything, but it didn't work out in the end. It's a shame as it was that close to the finish."
Zettel finished in a two-run combined time of 2 minutes, 36.22 seconds for her first victory of the season and seventh overall.
Miller was poised to take the lead from early pacesetter Buechel before he lost control. The American, who was unhurt, said he hit a bump approaching a right-hand turn in the closing S-bend and his right hip hit the snow before he slid off course.
"I couldn't see great and went a little bit too direct," Miller said. "I just missed the timing of it."
Janka finished in 2:32.23 over the classic 2.77-mile track, the longest on the World Cup circuit. Janka was 0.66 seconds faster than Manuel Osborne-Paradis of Canada, and Marco Buechel of Liechtenstein was third.
Janka's fourth victory of the season gave him the lead in the overall World Cup standings.
"Winning in Wengen is the dream of any Swiss skier," said Janka, who competing in the Lauberhorn race for only the second time.
He has 757 points, 68 more than Austrian technical specialist Benjamin Raich, who skipped the race.
Osborne-Paradis said he did not expect his podium finish after poor training runs in the week.
"I was having a lot of doubts this week," he said. "I have no idea how I was fast today. I took more risks."
The 80th Lauberhorn race weekend ends with a two-run slalom race Sunday.