Harlequins remain unbeaten in the Heineken Cup with the victory.
Quins took some time to subdue the visitors, but once Zebre picked up two yellow cards in quick succession it was a case of damage limitation as the home side scored seven tries and collected 18 points from the boot of Nick Evans.
"We were imprecise and made mistakes but it was ultimately a job well done," O'Shea said.
"We scored over 50 points in each of the two games against them. Before we first played them I read out their scores to our players and it showed that after 55 minutes of each game they had been in contention so they take some breaking down."
Zebre's challenge was not helped by their ill-discipline, with centres Daniel Halangahu and Gonzalo Garcia as well as flanker Filippo Ferrarini yellow carded.
"When I stopped looking the penalty count was 24-4 in our favour," O'Shea said.
"That's the fourth game in a row that sides have conceded over 20 penalties against us and it shows what teams are trying to do to stop us playing.
"Treviso are a good side but Zebre only came together in August so it's difficult for them to compete. We all want Italian rugby to be strong but they get three times as much money as we do from the ERC which I think needs addressing."
The bonus-point win ensured that Quins, who beat Zebre 57-14 when the teams met in Parma last week, only have to secure one point from their remaining two games to top Pool Three and hopefully secure a home draw in the quarter-finals.
"We want to be at home in the quarter-final in April. People say that we are stuttering along but we've won 13 out of 16 in all competitions," O'Shea added.
"We are unbeaten in Europe, top of the Premiership and have won both our LV=Cup games."
Zebre lock Josh Sole was magnanimous in defeat, which he believes serves as a wake-up call after competing well in the RaboDirect Pro12.
"Full credit to Harlequins, their scrummage power was awesome and they taught us a huge lesson in the past couple of weeks," he said.
"It's demoralising to give away so many penalties as at international level you are supposed to restrict it to under 10.
"It's a big step back for us as we were progressing nicely in the RaboDirect and should have beaten Scarlets, Cardiff and Ulster."
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