The Hammers travel to Manchester on Wednesday night for their rescheduled meeting with the Premier League champions, knowing a point would lift them out of the bottom three.
City go into the game without a win in their last two in all competitions but will be keen to make a statement following Uefa's decision to ban them from the Champions League for two seasons.
Moyes knows that his side will have to set up to frustrate, but says they cannot simply rely on being hard to beat.
The West Ham boss said: "It’s as big as it comes, isn’t it? We’ve got Manchester City and then Liverpool in the next two games so let’s not kid ourselves.
"But you have to play them twice, everyone has to play them twice. These are our two games the way the ball has come out and we get them together. We know they are hard, but then we will go and try to be difficult to play against, hard to beat, but in the same breath we know we’ve got to go there and try to pick up points as well so there’s a balance between both."
Moyes may still be in search of just a second League win since his return to the club, but the Scotsman is loving life back in the capital and expects to be around for far longer than his previous six-month stint.
"I really enjoyed it the other time I was here," said Moyes.
"It’s not taken me too long to settle. Obviously I have got a new group of players, I have eight or nine from my last time but I’ve really enjoyed it, but I want it to be a long stay. But I know what that means - you need to win, get results and that’s what my aim is."