The Premier League leaders make the trip to the League Two outfit with a place in the fifth round of the competition at stake.
Chelsea are widely tipped to come out comfortable winners at Greenhous Meadow, but Zouma believes that the tie will be more difficult than that.
"It will be a very difficult game because we know they will be very determined. We have to play as a big team with lots of determination of our own," the defender told the club's official website.
"We also have to concentrate very hard because if you don't do that you will lose the game. It's as simple as that. Lower league teams are very hungry and they want to make an impact against big players and big teams. It will be very difficult but we have to win."
Chelsea reached the fifth round of last season's competition before losing to eventual runners-up Sunderland.