Mark McCall's men scored nine tries - Duncan Taylor touching down twice - as Saracens ensured qualification in Pool 3 will go down to the wire after Christmas by taking maximum points.
Saracens, who won 39-10 against Zebre last week, continued where they had left off against the Italians as Farrell - starting for the North London club for the first time since the autumn internationals - slotted an early penalty.
It looked a very tall order for the whipping-boys of Pool 3, Zebre, to get anything out of the game and it got even harder after just four minutes with England wing David Strettle scoring his seventh try of the season after he was released by Ben Ransom.
Inevitably Farrell added the extras from the left-hand touchline as Saracens found themselves 10 points to the good with the game barely five minutes old.
Luciano Orquera had the opportunity to reduce the deficit for Zebre with a penalty attempt of his own after eight minutes but unfortunately he was unsuccessful.
The miss proved costly as Saracens put further daylight between themselves and their visitors. A period of sustained pressure and an attacking line-out resulted in Jacques Burger emerging from a pile of bodies to claim his side's second score. Farrell was this time unsuccessful with his kick at goal.
Zebre's openside Nicola Cattina did little to help his side out as he was sin-binned after 20 minutes for taking George Kruis out in the air allowing Farrell to kick deep into Zebre territory and Jamie George to rumble over for Saracens' third try of the afternoon.
Farrell kicked the extras to put Saracens in a commanding 22-0 lead with only a quarter of the game gone.
And after 26 minutes Saracens secured the bonus point as Chris Ashton and Taylor combined superbly for Richard Wigglesworth to score, Farrell again converting for the home side.
Orquera finally got the Italians on the scoreboard after 29 minutes with a well-taken penalty but it did little to ease the continuous Sarries pressure.
It took just five minutes of the second-half for Sarries to score their fifth try of the game, Ransom strolling over after a powerful-break and interchange between Billy Vunipola and George and Farrell converting.
Just minutes later Wigglesworth displayed quick-thinking from a tap penalty to set-up Taylor for Saracens' sixth score of the afternoon. The ever-reliable Farrell kicked the extras to make the score 43-3.
The strength of the two clubs was never more evident than when Saracens started to empty their replacement's bench in the final quarter - Lions Matt Stevens and Mako Vunipola, plus England international Alex Goode among those entering the fray.
After 62 minutes Saracens brought up their half century as Taylor went over for his team's seventh try of the game but he seemed to injure himself in the process, Farrell again converting.
After a hugely physical showing it seemed almost inevitable England No.8 Billy Vunipola would barge his way over a score and that's exactly what he did after in the final quarter as Zebre began to tire.
Jackson Wray was sin-binned for Saracens in the final stages but despite the numerical disadvantage there was still time for England wing Ashton to score try number nine for the home side.
- Sports & Recreation