The Parisians failed to advance beyond the round of 16 of the competition after losing on away goals to Manchester United following a 3-3 aggregate draw.
The victory helped them to maintain their lead on the Ligue 1 log with 74 points from 27 games.
And the former Stoke City striker, though yet to recover from last week's ouster, is delighted with the commanding display at the Stade Gaston-Gerard.
“That's the only thing we can do: keep playing, give everything for this club, for us, for the fans,” Choupo-Moting told Leparisien.
“Winning 4-0 was a good reaction, although we cannot erase what happened. It's still very, very bad. It's normal that it's still in our heads.
“It is very difficult to find the right words to explain what happened. It shows on the face of each player.
“It's hard, but we have to keep going. Thiago Silva and the coach spoke, we all discussed and we said to ourselves: ‘We must at least show a reaction ‘. That's what we did today [Tuesday].”
PSG play host to Marseille in their next Ligue 1 game on Sunday at Parc des Princes.