Winger Adam Byrne scored a hat-trick of tries as Leinster reclaimed top spot in the Pro 12 table courtesy of a 33-10 victory over Zebre at the Stadio Sergio Lanfranchi.
Leo Cullen's men endured a testing opening quarter in which they lost Mike McCarthy to a yellow card and then conceded the game's first try as Dries van Schalkwyk found the line for the hosts.
But they hit back through five-pointers from Tom Daly and Byrne to lead at the break and ran away with the game in the second half as Byrne took his personal tally to three and back-rower Jack Conan also got his name on the scoresheet.
The Scarlets, meanwhile, climbed into the top six thanks to a similarly comprehensive 27-3 win over Glasgow Warriors.
The in-form Welsh side had won their last four Pro 12 games and were set on their way at Parc y Scarlets by an early try from Will Boyde.
The visitors then failed to capitalise upon Alun Wyn Jones being sin-binned for collapsing a maul in the 25th minute as Jonathan Evans scored the Scarlets' second try just before the break.
Boyde then went in again early in the second half and Rhys Patchell added 12 points with the boot.
On a night to forget for Gregor Townsend's men, they saw Pat MacArthur and Brian Alainu'uese both sent to the bin during the second period as they were beaten on the road for just the second time this season.