Barca travelled to Lisbon still high from their thrilling 3-2 win over Sevilla on Saturday night that maintained their 100 per cent start to the new La Liga campaign.
Victory against Real Madrid at the Nou Camp on Sunday will see Tito Vilanova's men open up an 11-point gap over their arch-rivals, but ahead of flying out to Portugal this morning [Tuesday], Zubizarreta insisted that the Champions League was the only focus for the time being.
"These are two different competitions," Zubizarreta told reporters.
"Right now, we have to focus on the Champions League. Then on Wednesday we can think about the league again.
"It's still only October and there are a lot of points still to play for."
Previews of other Champions League Tuesday fixtures
Barcelona's win over Sevilla was their sixth on the bounce in La Liga, while they kicked of their Champions League campaign with a victory - albeit hard-earned - at home to Spartak Moscow.
Zubizarreta insists the run will have little impact on the Group G encounter at Lisbon's Estadio da Luz, but he nevertheless stressed the importance of getting good points on the board early on.
"Winning steaks are built game by game," he said. "The results have been very good up until now but on Tuesday we are starting from scratch once again.
"Previous results are a good reference, but we are always starting from zero.
"In a short tournament like the Champions League, and especially in the group stages, good results early on can avoid suffering nearer to the end."
Barcelona have been dealt a blow ahead of the game after midfielder Thiago Alcantara was ruled out for up to eight weeks after scans showed he suffered knee ligament damage in the win at Sevilla
His absence has been tempered by the return of Andres Iniesta, Carles Puyol and Adriano, all of whom have been named in Vilanova's travelling party but remain doubtful.
"Puyol, Iniesta and Adriano are three great players, and now we've also lost Thiago. But these things happen in football," said Zubizarreta.
We'll try to get them fit as quickly as possible and when they come back, they'll be coming back with their full potential."
Barca forward Lionel Messi is expecting a tough encounter against Benfica but insisted that the club's reputation means no match is ever straightforward.
"Each game is different. They are all tough," Messi told El Pais.
"We could not score against Granada for 85 minutes, against Spartak we almost lost.
"It gets more difficult each time. We want to attack and they sit back and look for our weak point.
"If they get lucky and manage a good counter-attack, they can make it very difficult for us."
Benfica also head into the match boasting the leadership in their domestic league after an unbeaten start to the season.
Jorge Jesus' troops have won three and drawn two of their Liga outings so far and kicked off their Champions League campaign with a goalless draw at Celtic.
The hosts, seeking their first win over Spanish opposition for 30 years, welcome back Pablo Aimar after the midfielder was ruled out of the 2-1 win over Pacos de Ferreira at the weekend with a right leg injury.
Oscar Cardozo misses out with a left thigh strain, however, meaning Lima - who scored both goals in Benfica's weekend win - is likely to lead the line up front.