The Italians claimed their first ever RaboDirect PRO12 away to Cardiff Blues in round three and set up this victory via Guglielmo Palazzani's early first-half try.
Matt Berquist hit three first half-penalties as Treviso led 9-5 at half time but nine points from the boot of Luciano Orquera handed victory to Zebre.
While at the other end Ulster moved up to fourth with an impressive performance to inflict just a second defeat of the season on league leaders Munster.
Ruan Pienaar did the damage collecting 19 points from the tee while Jared Payne and Darren Cave dotted down in the first half.
Munster hit back through tries from Ivan Dineen, Dave Kilcoyne and James Coughlan but came up short 29-19.
Meanwhile Leinster closed the gap to Munster to three points, but they were made to work hard for the victory by a spirited Connacht before Gordon D'Arcy's try secured the result.
Trailing 8-3 at half time after Fionn Carr touched down for Connacht, Leinster nudged themselves back in front via two Jimmy Gopperth penalties before D'Arcy's late try left Connacht bottom of the table.
Scarlets' losing run against Ospreys continued as Steve Tandy's men put in a fine defensive display to triumph 17-12.
Ashley Beck and Aisea Natoga dotted down in the first half and while Rhys Priestland kicked 12 points for Scarlets, seven points from Dan Biggar maintained Ospreys' third position in the league.
While on New Year's Day Cardiff Blues brought an end to a four-match losing streak with a 21-13 win over Newport Gwent Dragons - Leigh Halfpenny kicking 15 of his side's points.
Will Harries' try and eight points from the boot of Jason Tovey had appeared to get the Dragons back in the game having trailed 9-0 but Halfpenny and a drop goal from Gareth Davies kicked them back to victory.
It proved to be the only game on New Year's Day with Glasgow Warriors' home match with Edinburgh was postponed because of a waterlogged pitch.
TRY OF THE WEEKEND
Not content with getting himself on the scoresheet with a try for Ulster, Jared Payne then threw in a sumptuous break to set up his side's second try.
Receiving the ball in his own half, Payne threw in a cheeky dummy to break the Munster line before storming into space, offloading to Andrew Trimble to cut inside.
Darren Cave then ran across him in support, picking up the ball to crash over the line in the corner and Ulster pressed home their advantage.
BREAK OF THE WEEKEND
With Ospreys under pressure early doors, it came as some relief when Rhys Webb snuck his way through the Scarlets line to spark a tremendous break and eventual try for Ashley Beck.
Seizing the ball just inside his own half, the centre gobbled up the ground before feeding Sam Davies who took up the baton before returned the ball to Webb.
Webb was eventually hauled down just inches from the try-line but Beck was on hand to scoop up the ball and get over.
PLAY OF THE WEEKEND
Zebre's famous victory was set up from the start when a combination of Luciano Orquera's up and under and Dries van Schalkwyk's chip and chase down the line helped set up the only try of the match on 12 minutes.
With van Schalkwyk attempting to run onto his own kick, Treviso's Angelo Esposito tried to knock the ball into touch, but only succeeded in spilling the ball towards his own try line.
And lurking with intent was Guglielmo Palazzani who got the faintest of touches to score for eventual victors Zebre.
PLAYER OF THE WEEKEND
South African Ruan Pienaar was given place-kicking duties for Ulster's game with leaders Munster and the scrum-half didn't disappoint, turning in a man of the match performance.
With Paddy Jackson putting a series of impressive performances from the tee at fly-half in recent weeks, competition had hotted up between the two.
But Pienaar seized on his chance in the spotlight, missing just one kick all night as he slotted five penalties and two conversions for his 19 points - the total managed by the entire Munster team.
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