The 31-year-old is serving a four-match suspension imposed by the FA for racially abusing Queens Park Rangers defender Anton Ferdinand last season.
"It's going to be an interesting game," Zola told Goal.com. "I think the chances are 50-50 as Chelsea are in a good moment, Manchester United as well. So it's going to be a game in which the result is going to be tight.
"I think Chelsea is in very good form and playing quite good football and they will have a little advantage because they are playing at home. We will see what happens but I see Chelsea slightly with an advantage.
"Terry is a big player for them, he's a leader, he's one of the most inspirational players on the pitch, so he will be missed.
"But Chelsea has got a really good squad and they have players that can easily come into the game and into the team and do very well."
Zola played for Chelsea between 1996 and 2003 and is now the manager of Championship club Watford.