Kylian Mbappe struck twice and Pablo Sarabia scored for the second game in a row as holders PSG, who host Barcelona on Tuesday after winning the first leg 4-1, stayed on course for a sixth domestic Cup triumph in seven years.
Mbappe put the visitors ahead on nine minutes with a fierce strike into the top corner at the end of a counter-attack.
Sarabia doubled the advantage just before the interval by latching onto Julian Draxler's cross after another rapid break.
Mbappe then chested the ball into the net from Marco Verratti's cross to put the result beyond doubt in the 74th minute.
Verratti, returning from injury, played 75 minutes and Angel Di Maria came in as a second-half substitute after missing five games due to a thigh problem.
Elsewhere, RC Lens, who are fifth in Ligue 1, slumped to a 3-2 defeat at third division Red Star.
Lyon advanced by beating Ligue 2 side Sochaux 5-2.