Zabaleta believes Neil Warnock's side have already proved they are capable of beating top sides and is warning against complacency when the teams meet on Sunday.
"I think it is going to be a really difficult game because Leeds have already proved they can beat anyone on their day," he told City's website.
"They have beaten Spurs and Everton this season and it was only a couple of years ago they beat United at Old Trafford so we know they will give us a tough 90 minutes.
"They are bringing 6,000 fans and they will really lift the Leeds players and male plenty of noise. As we know, there are no easy games in the FA Cup, especially at this stage.
"Leeds are doing OK this season and they are a club who are set up for the Premier League so, like I said, we'll have to be at our best for this game."