Lewis McGugan scored against his former club to rescue a point for Watford in what was an open game that saw plenty of chances for both sides.
Zola acknowledged that such matches are entertaining for spectators, but revealed that it was too open for his liking and highlighted a weakness in his side's defence.
"It was one of those games which was good for the crowd and the TV but certainly not the managers," Zola told the Press Association.
"It was too open. We know we have to defend better than we are at the moment. But if you want to be offensive you can't be perfect at defending, it's a fine line."
Watford currently sit fifth in the Championship having won two and drawn two of their opening four fixtures.