The Parisians host the Blues in the first leg on Wednesday evening, with Ibrahimovic adamant that just reaching this stage of the tournament is a bonus for his team.
"Chelsea are the super favourites," he told reporters. "We have nothing to lose – Chelsea are a big team.
"We have a project which has been going on for two years, we're having a good season and everything we achieve now is a bonus. Chelsea have been implementing their project for 10 years and they have already won the Champions League and the Europa League.
"This match against Chelsea is a good test for us, but this doesn't mean the other games were easy. This is the way to improve - the tougher the games you play, the better you become."
Ibrahimovic is the second top goalscorer in this season's Champions League with 10 goals, three behind leading marksman Cristiano Ronaldo.