The Hornets are sitting in third after goals from Ikechi Anya and Nathaniel Chalobah, and Zola revealed he did not expect his youthful side to mount such a strong challenge this season.
"We're really playing well away from home. I'm delighted and I have to admit to being surprised by what these players are doing," he said.
"They're really performing to levels that are unexpected by me, considering that we're a young team that have just been assembled this year.
"They're making me very proud and I was delighted by this victory.
"It wasn't the same standard that we reached at the weekend (in a 4-0 win at Birmingham) but you can't do that all the time.
"We played some good football for large parts of the first half and deserved to be in front.
"But Ipswich came back strongly and we tired.
"We couldn't handle the ball as well as we had been, but we never gave up. We worked hard as a team and defended extremely well.
"We took our opportunities. They had opportunities and didn't and that was the difference."