In the closing minutes of the match and with only one goal separating the sides, substitute forward Zerbin came alive, initially tapping in Napoli’s second goal in the 84th minute at the far post before completing the brace two minutes later.
Napoli broke the deadlock after 22 minutes when Juan Jesus delivered a perfectly timed pass into the box for Giovanni Simeone to slot in from an acute angle.
Fiorentina forward Jonathan Ikone won a penalty just before half-time after being fouled by Mario Rui. However, Ikone sent his spot kick well over the bar.
The game took place in a partially-filled Al-Awwal Stadium in Riyadh, the capital of Saudi Arabia.
Inter Milan and Lazio are set to play on Friday in the other semi-final, with the final scheduled for Monday.
AAP