The Italian, who races in the series using special hand controls after losing his legs in a 2001 Champ Car crash, held onto victory despite a last corner attack from fellow BMW driver Jorg Muller.
It was his first international level victory since he won the Surfers Paradise Champ Car race in 1998. But Zanardi was worried that he had lost the victory moments after the finish because there was silence on his radio.
"I didn't hear anything on the radio, so I thought something happened. That for some strange reason they disallowed my victory," Zanardi told Gazzetta dello Sport.
"Then I looked at the fans on the grandstands and they looked crazed. But it turned out that the people in my team were crying and hugging each other, they were overcome by joy."
Zanardi also says how he used mind techniques to get through the race, and visualised his family members in an effort to win, after converting his pole position to an early lead.
"I told myself I couldn't afford any errors," he said. "I sprang as if a slingshot catapulted me forwards. The others attacked me and I resisted. I liked myself very much. I was perfect, like in the old times.
"As the laps went on I could see the names of the people following me changing. At one point they started signalling me that the similar BMWs behind me. That was disturbing.
"But I thought it was up to them to pass me, while I only had to avoid making mistakes. As the kilometres went on the tension, the exhaustion and the panting were about to catch me out: I just couldn't stand finishing second or third.
"I told myself: Come on Alex! [My wife] Daniela is in the pits, don't disappoint her. Nicolo [my son] is watching you on TV.'
"I saw the BMWs growing bigger and bigger in the mirrors. At one point Jorg Muller got on my left side while on the right side there was Priaulx. I risked being squashed and becoming a slice of ham. But I stayed in front and won."
Zanardi will now return to testing in his pursuit of the Italian Touring Car Championship, and is scheduled to test at Varano today.
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