The game's defining moment of brilliance looked to have come just before half-time as Hornets playmaker Almen Abdi, one of a contingent of players on loan from Udinese, converted a delightful free-kick for his 10th goal of the season.
The Hornets could at that point thank goalkeeper Jonathan Bond, making his full league debut, for still being on level terms having made an impressive double save, while Ikechi Anya then somehow failed to double the visitors' advantage midway through the second half.
But with the in-form Hertfordshire outfit staring at another three points to strengthen their grip on second place in the npower Championship table, Sako popped up to convert Matt Doherty's long throw-in to make it 1-1 at Molineux.
"It's disappointing because I didn't see it coming, I thought we were in control of the game," Zola said. "But I believe the difference wasn't the goal conceded it was the second goal we didn't score. We had opportunities.
"We were controlling their set-plays, something which could have been a problem because they kept putting a lot of balls forward, so because of that I thought it was finished. I didn't see it, honestly I didn't see the last goal coming.
"I was already thinking the game was won and their late goal was a shock for me as it was for all the team.
"But I repeat we obviously have to be more clinical when we have opportunities because 1-0 away from home is not enough."
Yet, despite the late setback, the Italian refused to be too downbeat, with his side unbeaten in six matches and having won seven of the last 10.
"We've come into the game from three successive victories, in February we won four games out of five, so I can't complain too much because we've dropped a point against Wolves away," Zola added. "There are a lot of games not only for us but for the others (promotion rivals) and it will be difficult for them as well."