City have so far beaten the Londoners twice, in the Community Shield and at home in the league, while they also drew with the Blues at Stamford Bridge.
But full-back Zabaleta insists those results mean nothing as they continue to prepare for the Wembley showdown.
“Our total focus right now is Chelsea, who we know will be a very tough opponent, but we are in a good moment form-wise and if we play at our best we will have a great chance,” he said.
“Those results don’t mean a thing – this is a different game and Wembley is a special place to play football and it gives everyone and extra motivation.
“We will prepare properly for Sunday and hopefully, things will go our way.”
Zabaleta has also dismissed claims whoever wins Sunday’s game will have an easy ride in the final against either Premier League strugglers Wigan or Championship side Millwall.
He added: “We are aware people are saying our semi-final is going to be ‘the final’, but that is disrespectful to Millwall and Wigan. Nobody wins a trophy for winning a semi.
“The same thing happened when we played United in 2011 because Bolton and Stoke were in the other game.
“We need to beat Chelsea and then we can think about who we will play. It doesn’t matter that Wigan and Millwall aren’t considered top teams in that they are challenging regularly for major honours because in one game, anything can happen and it would all be about who plays the best.”
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