City are all but guaranteed to be playing at Wembley after thrashing West Ham 6-0 in the first leg of their last-four clash a fortnight ago.
With such a commanding advantage, manager Manuel Pellegrini is likely to rest a number of key players at Upton Park but Zabaleta claims there will be no complacency.
The right-back, one of those who may be given a night off, said: "It doesn't matter about the first leg.
"We have to go into that game thinking it's a new game, even though we have six goals.
"We need to try and win it, like we are doing in other games at the moment. We are winning games and working hard.
"West Ham are in a tough moment, they are at home and will want to win it. So we need to take it seriously and we will."
City's demolition of the Hammers increased the scrutiny of manager Sam Allardyce, coming just three days after the London side crashed out of the FA Cup with a 5-0 loss at Nottingham Forest.
They did recover to win in the Barclays Premier League for the first time in seven games with a 2-0 success at Cardiff but Saturday's 3-1 loss to Newcastle left the pressure on.
West Ham remain in the bottom three of the table and the return clash against City offers the chance to restore some pride ahead of a tough trip to Chelsea.
City manager Manuel Pellegrini is also taking nothing for granted.
He said: "We have to play on Tuesday. The semi-final is not finished.
"Of course we have made an important step (towards the final) but we must see which players will play and the way we will do it."
Two players who could come into the reckoning for City are striker Stevan Jovetic and midfielder Jack Rodwell.
Both have been hampered by injuries throughout the season but are thought to be close to fitness.
Montenegro forward Jovetic has almost become the forgotten man since his £22million move from Fiorentina last summer.
While fellow forwards Sergio Aguero, Alvaro Negredo and Edin Dzeko have scored 58 of City's 103 goals this season between them, Jovetic has claimed just two from five appearances.
Hamstring and calf injuries have been his main problems but Pellegrini has repeatedly stressed his importance to the squad for the second half of the season.
England international Rodwell has made just three starts this season after more of the hamstring problems that have blighted his career.
When asked if either had a chance of playing at West Ham, Pellegrini said: "Maybe, we will see. On Monday we will decide."
City, who remain in contention to win four trophies, are in formidable form.
Pellegrini's men are unbeaten in 17 games, 15 of which they have won and Saturday's 4-2 defeat of Cardiff took them through the 100-goal barrier in just their 34th game of the campaign.
Winger Jesus Navas, who scored City's second against the Welsh side, said: "It is really nice to see the team scoring so many goals.
"We are working very hard, not only attacking but in defence and that is why we are getting these results.
"We are very confident. The manager is helping us a lot. I think we are in a good way and we are working really well.
"We have these targets and we have to challenge for titles."