Sears has been at Selhurst Park all season and was expected to remain there until the summer but the suspension of Guillermo Franco, and injuries to Carlton Cole, Luis Boa Morte and Zavon Hines, plus Dean Ashton's retirement, have left the West Ham manager short of attacking options.
Related ArticlesWest Ham ownership saga set for conclusionPremier League: transfer window guideWest Ham linked with Adrian MutuTottenham 2 West Ham 0Tony Fernandes circling West HamSport on televisionSears did not manage a single goal during his spell with Palace, although he infamously had a perfectly good effort ruled out at Bristol City in August after the ball rebounded back out of the net.
Sears, who may start on the bench, said: "It feels good to be back, it was brilliant to see everyone again. It is a different type of football at Palace where I played a lot on the right wing. There was not a minute of it that I didn't like and they have helped me along. It has all been part of my learning curve.
"This a great game to come back to. You don't get any bigger than Arsenal in the third round of the FA Cup at Upton Park. The scene is really set and I just want to do as well as I can."
Zola, who is still unsure whether he will be able to spend money in the transfer window, said: "The youth policy is working and in difficult circumstances. The kids are doing very well. James Tomkins is one of the very good youngsters, also Jack Collison and there are others.
"We are moving forward positively. Obviously there are difficult moments because the table is not as ideal as I would want, but we will improve that.
"Against Arsenal, we've still got a few options, but we want to honour the competition so we're going to try to win the game. We're playing home against Arsenal and we will have a go. I know that maybe the FA Cup not a priority but we will be there and up for it.
"I think it's a good opportunity, we'll have the possibility to play some players and make some things that I want to make. It's an opportunity I will use well."
Zola, an FA Cup winner with Chelsea in 1997 and 2000, knows the size of the task, believing that Arsenal are back in the title chase.
"Why not? They have also a game in hand and the championship right now doesn't look as if there is one team who will dominate. Even Chelsea, who in my opinion are the best team, are struggling. It's not easy, so yes they have a chance.
"Plus, I like the way they play, I like the spirit they have and also I like the kind of management they have and I'm not saying that now, I've always said that. It's something that West Ham would like to do the same. It will be an interesting championship."