Federico Dimarco delivered an excellent cross into the box and Thuram seized the opportunity to score his debut goal for the club in the 23rd minute with a powerful diving header.
Martinez doubled Inter’s advantage after 53 minutes when he was played through by Thuram at the edge of the box, with the unmarked captain easily putting it into the net.
Hakan Calhanoglu made it 3-0 by converting a penalty five minutes later, following Fiorentina keeper Oliver Christensen’s foul on Thuram.
Martinez netted his second goal of the match and his fifth of the season with a one-touch finish inside the box from a well-placed cross in the 73rd minute.
(Reporting by Tommy Lund in Gdansk, editing by Pritha Sarkar)