Glasgow Warriors were handed just their third Pro14 defeat of the season against Scarlets on Saturday, while Benetton Rugby and Cheetahs both edged tight thrillers.
Warriors lead Conference A, but they were beaten 26-8 by second-placed Conference B outfit Scarlets in Llanelli.
Rhys Patchell went over twice and Leigh Halfpenny kicked eight points to keep the pressure on conference leaders Leinster, who also won.
Struggling Zebre were no match for the Irish side, failing to score a try as they went down 41-6, James Lowe and Max Deegan each touching down twice.
Benetton are running out of time to reach the play-offs but they did their chances no harm with a bonus-point win over Dragons, although they almost let a commanding lead slip.
The Italian side led 26-6 at the break, but they settled for a narrow 29-27 victory as Dragons fell short in their fightback.
Sibahle Maxwane scored twice as Cheetahs won by the same scoreline against Cardiff Blues, while Munster were 39-22 winners at Conference B basement side Southern Kings.
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