Nacewa touched down in the 61st minute and, with Jonathan Sexton converting for a personal points haul of 16, completed a sequence of 24 unanswered points with Zebre level at half-time.
Fionn Carr and Dominic Ryan also scored in the second half to take the game away from the Italian outfit and add to tries from Tom Denton and Fergus McFadden in the first 40.
Sinoti Sinoti's score and a try, a penalty and two conversions from Daniel Halangahu kept Zebre in contention at 17-17 at half-time but they contributed just Carlo Festuccia's effort after the break.
Leinster moved back above Glasgow into second in the RaboDirect PRO12 table courtesy of the win with one point separating the two ahead of the final round of the regular season in two weeks time.
Sexton, back after completing his rehabilitation from injury, kicked the first points of the game with a penalty in the third minute before Halangahu returned the favour for Zebre.
However within four minutes Leinster scored the first try of the game as, with the ball recycled, Andrew Goodman fed Denton to cross in the corner with Sexton slotting the conversion.
It took Leinster just another five minutes to grab their second try as this time a great break, dummy and pass back inside from Sexton allowed McFadden to touch down.
Sexton kicked his second conversion however Zebre responded through Sinoti with the Samoan wing dancing through the Leinster defence and Halangahu converting to make it 17-10.
Halangahu then did it all himself to level the scores at 17-17 on the stroke of half-time however Zebre were to add just the sole try from Festuccia after the restart.
Sexton quickly put Leinster back in front with a penalty before providing the kick that led to their third try as the ball bounced kindly for Nacewa who passed to Carr to score.
It was again converted by Sexton with Leinster grabbing their fourth try just before the hour through Ryan who had moments earlier had a score ruled out by the Television Match Official.
That completed the bonus-point win with Nacewa getting in on the act himself moments later after a lovely pass from Brian O'Driscoll with Sexton maintaining his 100 per-cent accuracy.
Leinster had now scored 24 unanswered points however Zebre collected the final points of the game as Festuccia went over seven minutes from time for the Italian outfit.
Luciano Orquera hit the post with the conversion before Zebre's final try scorer Festuccia was shown yellow two minutes from time as it ended 41-22.
|Zebre Score Card|
|Leinster Rugby Score Card|