But the victory was helped by the dismissal of Hull's Craig Fagan in the second-half and, after the visitors had used all three of their substitutes, the loss of City captain Anthony Gardner with a serious leg injury.
"It is too early to say but the last two results have been big for us not only in terms of points and position in the table but in terms of confidence for the whole team," said Zola.
"But we have some massive games coming up, especially at home, and we have to stay focused. It is a very good indication today that it is not over yet.
"When there was a little bit of doubt in the game it was because we allowed those doubts. I am talking about the last five minutes of the first half when they came back and had a couple of chances.
"It was because we made it easy for them. I think we controlled the game very well. We are getting better and better. It was an excellent game for us.
"We are looking better but need to keep a focus. This is a team that when it plays with confidence, can be a surprise.
"We don't know whether 37 or 38 points will be good enough to be safe. There have been some surprise results like Tottenham losing against Wolves, but we will try and get 40 if we can.
"I must say the whole team performed very well. It was a team performance, especially the way we started the game was fantastic. We needed to set the tempo straight away and the way we started was excellent. It made the game easier for us."