Zak O’Sullivan made his car racing debut in the 2019 Ginetta Junior Championship. In the first ten races of the season, he scored five podiums. During the second half of the season, he won two races and had nine consecutive podium finishes which resulted in him finishing 2nd in the championship. For 2020, O’Sullivan moved up to the F4 British Championship to drive for Carlin and with a strong season finished the season 2nd in the championship after a close call finish. O’Sullivan remained with Carlin for 2021 and progressed to the GB3 Championship. With 7 wins and 7 podiums, O’Sullivan clenched the title in the final round of the season. 

O’Sullivan reunited with Carlin for 2022 and moved up to the FIA Formula 3 Championship. He scored 2 podiums and a pole position and finished the season 11th in the championship. For the 2023 F3 season, the British driver makes the move to Prema Racing.