Sexton set them rolling with a penalty before Leinster exploded into life with a late flurry, Andrew Conway and Sexton going over and the out-half adding two conversions.
With Leinster on their way to victory Sexton was replaced at half-time by Ian Madigan but Zebre had other ideas with full-back Tito Tebaldi stretching over to touch down soon after the restart and Daniel Halangahu adding the extras.
McFadden took up kicking duties and landed a 40-metre penalty before bursting forward to cross, converting the try for a 27-7 lead.
Cian Healy then crossed the whitewash from the back of the ruck to seal the bonus point and man-of-the-match McFadden added Leinster's fifth and his second try.
Zebre started the better side but just before the half-hour mark Leinster got the first points with Sexton landing a penalty from right in front of the posts to make if 3-0.
It was not long before the hosts got the opening try, a great piece of play by McFadden setting up Conway with 34 minutes gone.
McFadden ran towards a high ball and took it on the run, despite the awkward bounce, before spinning his opponent and being dragged down on the 22, with play going out to the right for Conway to go over in the corner.
Sexton added the extras with Quintin Geldenhuys sent to the sin-bin before Sexton got another conversion after touching down himself with two minutes to go to make it 17-0, the try given after being referred to the Television Match Official.
The Italians were again in the ascendancy at the beginning of the second half and this time they were rewarded with Tebaldi escaping Leo Cullen's attentions to stretch over while on his knees and score, the TMO having a long look before awarding the try.
Halangahu's conversion brought Zebre to within ten points with 51 minutes gone, but three minutes later McFadden slotted a long-range penalty to settle his side's nerves.
Madigan then found Gordon D'Arcy out wide who offloaded to McFadden to race clear and touch down before adding the conversion, Leinster leading 27-7 on the hour.
With eight minutes to go Leinster claimed the lineout and piled forward, Healy picking up the ball and going up the blindside to cross for the bonus point, though McFadden missed the conversion.
It did not take long for the fifth try to arrive, McFadden grabbing his second of the evening after picking up Madigan's cross-kick and racing clear to dive over.
This time his conversion struck the bar to leave the scores at 37-7.
|Leinster Rugby Score Card|
|Zebre Score Card|