Pirlo, 41, was sensationally appointed Juve coach on Saturday after the Serie A winners sacked Sarri following their Champions League last-16 exit at the hands of Lyon.
Former Juve midfielder Pirlo, who was only recently named the Under-23s boss in Turin, will surprisingly have his first taste of senior coaching with the Bianconeri.
Zola worked as an assistant to Sarri at Chelsea in 2018-19 and he told Sky Sport Italia: "I'd be lying if I said I wasn't surprised by this.
"It's fascinating and if the project works, it'll go down as a huge success story for the club. It's not an easy job, though, as Juventus are asking to win in a certain way.
"This is a courageous move from the club and based on the quality of the man, but Pirlo will need their support going forward. It's not simple, but I do think he can have real success."
Pirlo left Juve in 2015 after the Bianconeri, who had been chasing the treble, were beaten 3-1 in the Champions League final by Barcelona.
He spent two years in MLS with New York City before calling time on his playing career.
The 2006 World Cup winner is a six-time Serie A champion, having won two Scudetti with Milan and four with Juve. He twice triumphed in the Champions League as a Rossoneri player, in 2003 and 2007.
England footballers Bukayo Saka, Marcus Rashford and Jadon Sancho were subjected to racist abuse online after their penalty shoot-out misses in the Euro 2020 final.
Those failures from the spot helped Italy to land their second European Championship triumph.
There have been calls for the likes of Twitter, Instagram and Facebook to police their platforms more effectively, with 19-year-old Saka urging the three tech giants to each step up their game.
Former Italy and Chelsea forward Zola told Stats Perform: "Racial abuse is unjustifiable, unforgivable and unacceptable. I reckon that youngsters have to understand very quick that not all people they come across on social media are good.
"They use it to provoke, insult, abuse and vent their daily frustrations. We have to get used to it and learn how to isolate from this. Especially young people who are famous like footballers.
"These are all unjustifiable attacks but we have to learn how to isolate from it all because these bad people will always be there."
Zola, who enjoyed a seven-year spell at Chelsea and collected 35 caps for the Azzurri, explained there is a "dark side of social media".
He said: "Many people use [social media] in an absurd way and can cause damage to kids who are on social media and are not ready to accept all this.
"If you are into social media, you have to be aware these can be used by people to insult and destabilise. This is the dark side."
