The Swede netted the second from the penalty spot in the 36th minute after Thiago Silva had put the hosts ahead following a 10th-minute corner that was parried into his path.
Ibrahimovic initiated the move that led to a third by Thiago Motta six minutes after the break, set up Edinson Cavani for the fourth and wrapped it up himself on 64 minutes to bring his season's league tally to 17 goals.
PSG top the table on 50 points from 21 games, five ahead of Monaco who won 2-0 at mid-table Toulouse thanks to a first-half goal Layvin Kurzawa and a splendid overhead kick by substitute Lucas Ocampos two minutes from time.
French champions PSG, who have scored 15 goals in their last four matches in all competitions, were never threatened by Nantes and captain Thiago Silva said they would get their chance on the European stage if they produce the same kind of performances.
"The boys have made a lot a great things tonight. We have to continue the same way and hopefully we'll play like that in the Champions League," he told French channel Canal Plus.