Striker Forestieri, 23, scored his first Watford goal at Huddersfield last season and he returned to inflict more damage on the West Yorkshire club, scoring the opener for his side in Saturday's 2-1 win.
During last season's corresponding fixture Forestieri provoked the fury of home fans by going to ground at every opportunity, but those antics were not in evidence on his return and Zola said: "No one has ever doubted his qualities but he has to use them in the right way.
"The Huddersfield fans remember him but he reacted well. He also stood up all the time!
"He has all the tricks and the pace but he is still young. He is improving and has huge potential."
Danny Ward's flicked header gave Huddersfield a 17th-minute lead from Adam Hammill's right wing cross but the advantage lasted just over a minute as Forestieri hit back immediately.
Troy Deeney played the ball out to Davide Faraoni who centred for the unmarked Forestieri to drive home into the bottom corner.
Two minutes before the break Watford scored what proved to be the winner.
Hammill's needless foul on Forestieri conceded a free-kick just on the edge of the box. Lewis McGugan's strike was parried by Alex Smithies but he could not hold the ball and Daniel Pudil slotted home.
Watford had several good chances to seal the points in the second half but Forestieri, McGugan and Josh McEachran were wasteful.
Zola added: "It was a good performance but we had so many chances in the second half we should have killed the game.
"Forestieri was the best player on the pitch. He was quite a handful, holding up the ball and creating space. It's just a pity we didn't score a third goal."
Huddersfield boss Mark Robins said his side needed to show more belief.
"For the first 20 minutes we showed how good we are," he said. "But after that Watford came at us.
"We gifted the two goals and were on the back foot after that. For their first goal they broke really quickly and the finish from Forestieri was Premier League quality.
"We have to believe in ourselves, keep the ball better and be patient.
"We have lost our unbeaten home record to a good side."
Robins brought on 18-year-old academy midfielder Duane Holmes for only his third appearance at half-time.
He is taking it carefully with the teenager and said: "He needs the experience and this was another 45 minutes under his belt. He made a difference when he came on and eventually he will start hurting players.
"We will keep looking at him and see how he develops."