Juventus' Pirlo controls the Italian midfield and his partnership with Mario Balotelli is the big threat to the Asian champions in Wednesday's Group A game, Zaccheroni said.
"We are going to focus on Pirlo and Balotelli but not exclusively, as they have great players all over the field," the 60-year-old Zaccheroni said.
"But clearly that ... axis linking Pirlo to Balotelli is important for Italy's game and when they have the ball we will aim to pressure them.
"It will be important for us to close them down and make it harder for Balotelli to receive the ball and force Pirlo to hold on to the ball longer and look for another player to pass to."
Zaccheroni, who took over at Japan in 2010, said he felt his side had been overawed by the occasion in their opening 3-0 loss to Brazil, something he would be watching for on Wednesday.
"If in the first few minutes the Japan I see is the usual Japan I know I will try to push on the accelerator but if I see the team is timid once again then I will have to change things to try and force them to take the initiative," Zaccheroni said.
"Clearly on paper Italy are the stronger team.
"But sometimes you meet a stronger team that is not having one of their best days and on those days you need to be ready to seize the opportunity."
Japan are desperate for points after their opening loss and Wednesday's game could be make or break for their tournament.
If they lose and Brazil avoid defeat to Mexico in Wednesday's earlier match, they will be knocked out.
The Italians beat Mexico 2-1 on Sunday.