The two-time champions will need to do what they haven't done yet in the competition – win on their travels – after a second successive away defeat ensures they are now scrapping for their lives in the European competition.
The 5,000 Munster faithful in the 15,288 crowd did their determined best to drown out the insistently loud and annoying tannoy that blared music at every stoppage – and Zebo has declared that he and his team are equally resolute in chasing down qualification.
"Absolutely," said Zebo, a revelation at full-back following an early injury to Felix Jones which caused so much initial confusion in their ranks that they conceded their only try.
"There are two other big teams vying for one position. We need to go out and win our next two games. We can't really concentrate on anything more than that.
"It is still in our control. We still believe that we can get out of this group, so yeah, it is going to be all or nothing in the next two games."
Otherwise, they will simply be scrambling for a best runners-up slot.
"After four games, you want to have things in your own hands and control your own destiny," said Saracens' former Ulster coach Mark McCall.
"We have Racing away and they're right back in it. They have to go to Thomond Park.
"There'll be a few twists and turns in this group. But we know that if we win twice, we'll be through."
Asked if it would be difficult to qualify from this position, Munster coach Rob Penney was non-committal yet appreciative of the hardships involved in coughing up two defeats in their opening four games in a tight pool.
"I don't know," he mused. "We've still got the ability to get 10 points. Who knows what will happen in the next two games. There's a lot of rugby to be played.
"I'd be very optimistic that the group of boys that we've got will put themselves in the best possible place to be able to qualify."