Without a win in their first three league games of 2023, Bayern came into the game under huge pressure to reach the quarter-finals of the German Cup for the first time in three seasons.
Choupo-Motingen calmed the visitors’ nerves in the 17th minute and they had a second on 30 minutes when Bayern veteran Thomas Mueller found teenage striker Jamal Musiala and fired the ball across the face of goal to make it 2-0.
Winger Leroy Sane scored the third goal with a minute left in the first half, off a glancing assist from former Mainz striker Choupo-Moting.
Choupo-Moting’s goals and assists kept the Hamburg striker’s outstanding record high, with him now netting nine goals and five assists in five DFB-Pokal games for Bayern.
Canadian full-back Alphonso Davies, who came on for Cancelo with 20 minutes left, scored a fourth late in the game, off a floated assist from Dutch centre-back Matthijs de Ligt.
Mainz had a number of half-chances in an increasingly heated second half, with centre-back Alexander Hack sent off for a second yellow card, along with Bo Svensson, who was shown a straight red for arguing with the assistant referee before Davies’ goal. .
– Werner in goal –
In Tuesday’s opener, former Chelsea striker Timo Werner scored late on to help RB Leipzig beat German Cup holders Hoffenheim 3-1.
Werner, who returned to Leipzig from a two-year stay at Stamford Bridge in August, endured a difficult night and was caught offside on several occasions.
However, he got the timing right in the 83rd minute, latching on to a pass from Danish forward Yussuf Poulsen and beating Hoffenheim goalkeeper Oliver Baumann to seal victory for his side.
Leipzig, who are unbeaten at home in the league this season, struck after eight minutes, with Swedish striker Emil Forsberg catching Baumann napping to squeeze home a long-range shot.
Leipzig doubled their lead before half-time, Austrian midfielder Konrad Laimer collecting the ball on the return before curling a powerful left-footed shot into the corner of the net.
Kasper Dolberg headed in a superb cross from former Leipzig full-back Angelino in the 77th minute to cause some nerves for the home side in the closing stages.
However, Werner scored his fourth goal of the cup campaign with just over five minutes remaining.
“We showed that we want to go further in the competition,” said Forsberg.
“We played a good first half, we were very focused. We could have sealed it earlier, but it was a well-deserved victory.”
Former Borussia Dortmund midfielder Thomas Delaney, who signed for Hoffenheim on Monday, told Germany’s Sky that “we have a good squad, we have great players, but we lack confidence at the moment.”
Hoffenheim captain Baumann agreed, saying his pressure-free side hoped to build confidence with a better result in the cup.
Hoffenheim are 13th in the league, three points off the relegation play-offs, and Baumann said the team had to admit “we are in a relegation battle”.
“We’re almost losing and that really bothers me.”