Giovanni Brignardello also arrives at Vicarage Road as head of sports science, while fitness coach Ade Mafe and Giorgio Gasparini, who was head of rehabilitation, join Corradini in leaving the Hornets.
Zola told the club's official website: "They all did a good job and I would like to thank them personally for what they did. We wish them all the best for the future."
On Porcu and Brignardello, Zola added: "Gianni's credentials come before him.
"He has always worked with good teams and he's doing a good job so far. In the first few days he has confirmed all the good things that have been told to us.
"I look forward to working with Bastiano in the future and know he will add quality to our staff at Watford."