The in-form German player registered a straight-set victory over Daniil Medvedev to reign supreme in Turin.
Daniil Medvedev won the match against Casper Ruud in straight sets and recorded an impressive score of 6-4 6-2.
The Serbian World No.1 defeated Cameron Norrie to finish the round-robin stage with a perfect 3-0 record.
The German will face World No.1 Novak Djokovic in the semi-finals on Saturday after the Serbian secured top spot in Green Group.
The World No.2 downed Hubert Hurkacz in his opening match and backed that up against the German.
Zverev, who famously won the 2018 Nitto ATP Finals title, will compete at the season finale for the fifth straight year.
Daniil Medvedev, who won the US Open in 2021, is the defending ATP Finals champion having won the title in 2020.
The German has been on an impressive run of form lately, as he now holds a 25-2 record since Wimbledon.
The second seed, who earned both his 50th tour-level victory of the season and 300th tour-level career win this week, was at his impressive best on Saturday.
Andy Murray beat world No.10 Hubert Hurkacz at the Erste Bank Open in Vienna.