Holders Bayern Munich beat second division Alemannia Aachen 4-0 to survive a night that saw both Kaiserslautern and Hoffenheim dumped out of the German Cup by second-tier opposition.
Bayern took the lead after 25 minutes with Mario Gomez tapping in a Luiz Gustavo low cross and Thomas Mueller doubled the lead when he fired in through the legs of keeper David Hohs in the 75th minute.
Muller struck again four minutes later and Arjen Robben, who came on as a substitute, completed the rout in the 88th minute.
Lowly Energie Cottbus beat Hoffenheim 1-0, with the Bundesliga team giving a debut to new signing Ryan Babel. The Dutchman missed a great chance to give his side the lead, but was made to pay later on as Shao Jiayi scored with six minutes to go.
Kaiserslautern also fell, by losing 2-0 to Duisburg. The Bundesliga 2 side are hopeful of gaining promotion to the top flight and impressed, despite having little possession. Branimir Bajic put the underdogs ahead with a fine shot after latching on to Stefan Maierhofer's pass, before Goran Sukalo doubled their advantage after the break.
They are joined in the semi-finals by Schalke, who beat Nurnberg on Tuesday.