PSG, who wrapped up the Ligue 1 title last month and are now 30 points clear of second placed Olympique Lyonnais, suffered heartbreak in midweek when City won the second leg of their quarter-final 1-0 following a 2-2 draw at the Parc des Princes.
They responded emphatically, however, with Blaise Matuidi, Edinson Cavani, Angel Di Maria and Maxwell also getting on the scoresheet in a convincing victory over mid-table opponents.
The win moves Laurent Blanc's side on to 86 points and needing one more win to equal the club's all-time record total for a single season in the top flight.
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"The victory doesn't help us forget the defeat against Manchester City, but we have to keep going, because the only way we will get over it is by winning," said PSG defender Marquinhos.
Top scorer Ibrahimovic struggled to assert himself against City, but opened the scoring in the 12th minute when his long-range shot evaded goalkeeper Remy Vercoutre, who should have done better.
The strike was the Swedish frontman's 31st of the Ligue 1 campaign, his biggest haul in a single league season during his dazzling career.
Matuidi added another in the second minute of first-half stoppage time, before turning provider after the break as he duped Vercoutre with a cut-back, leaving Cavani to bury the ball into the open net.
Di Maria added insult to injury when he sent a delicious chipped effort over the advancing Vercoutre in the 52nd minute, while Ibrahimovic's fine volley and substitute Maxwell's close-range effort compounded the visitors' misery.
"Is Ligue 1 too easy? I mustn't say that in front of the TV cameras," added Marquinhos.
The beleaguered Vercoutre, whose side remain ninth on 46 points, said he would not be watching a video of the match.
"I'll try to forget it," he said. "Tonight, I'll have nice beer, sleep well and try not to have nightmares about what happened here."
St Etienne moved level with fourth-placed Nice on 54 points in the hunt for a European spot after Nolan Roux's late effort secured a 1-0 win at Bastia.
Third-placed Monaco host Marseille, who are only six points from the drop zone, in one of three matches on Sunday.
(Writing by Ed Dove; Editing by Toby Davis/Alan Baldwin)
