In 2002, he decided to focus on the Telefónica World Series, which he won. Zonta was then hired as test driver for the Toyota F1 team in 2003, retaining the position in 2004. Toward the end of the season, the team sacked Cristiano da Matta from a race seat, and Zonta drove in four Grands Prix. In Belgium, he was running in fourth place three laps from the finish when his engine failed. In Suzuka the team hired Jarno Trulli and Zonta had to sit the event out, but the team allowed him to compete in his home race, the Brazilian Grand Prix, which he finished in 13th. He continued as a test driver for Toyota in 2005, alongside veteran French pilot Olivier Panis. At the US Grand Prix later that year, he stood in for the injured Ralf Schumacher and took his place on the grid, only for Toyota, like the other six Michelin-shod teams, to withdraw from the race due to safety concerns. 2006 saw Zonta continue with Toyota as the team's third and test driver. He was confirmed as test driver for the Renault Formula One team for the 2007 season on 6 September 2006.