The Rossoneri need only to avoid defeat at home to their Champions League Group H rivals to progress to the last 16 and the centre-half is looking forward to the San Siro showdown
The Colombian netted in between efforts from Kaka and Mario Balotelli as the Rossoneri claimed a crucial win in Glasgow that kept them one point ahead of qualification rivals Ajax, who upset Barcelona in Amsterdam.
With the Dutch champions due in Milan on matchday six, Zapata is now looking forward to what is effectively a winner-takes-all clash at San Siro.
"I'm happy to have scored today - it was a great win and we deserved it," Zapata told Sky Sport Italia.
"We came here to play and win. Now we face Ajax at home and will do anything to win."
Milan had gone into the game without a win in seven games in all competitions, putting a huge amount of pressure on both coach Massimiliano Allegri and his players, who were both targeted by frustrated fans after Saturday's 1-1 draw at home to Serie A rivals Genoa.
Consequently, Zapata is now hoping that the Rossoneri can now kickstart their domestic campaign when they travel to Catania on Sunday.
"During these last few days has been difficult for us," he added. "We have now given an answer in Europe and we hope to do the same in the league.
"Did we play for Allegri? We played for us - for Milan."