While lining up at the Venice Marathon on Sunday he decided not to try and win the race, but to complete the gruelling 26 mile course alongside 17-year-old quadriplegic Eric Fontanari.
Eric had been desperate to take part in the marathon despite having only minimal use of his arms, and after an encouraging training run he had high hopes.
But foul weather conditions almost ended his dream: with high winds and rain lashing the course, he was barely able to continue, and Zanardi began to push him along while still keeping his own hand bike going.
But the trials were only just beginning.
"It's been a crazy adventure," Zanardi said later.
"Eric began to suffer from the cold with muscle spasms, and could no longer hold his bike which was veering off to the left. At that point I realised that there was no way we would get to Venice in that condition."
Rather than give up, though, Zanardi had a brainwave.
"I decided to attach the front of Eric's bike to the back of my bike using a rope I found in a rubbish bin by the side of the course. We took the front wheel of Eric's bike off to link it on to mine, and off we went. We looked like the A-team!"
Zanardi proceeded to propel both himself and Eric along, but still things kept on going wrong: under the strain my gears broke, sticking me in a high gear that was almost impossible to keep going.
"But miraculously I found some tape to fix it up enough to get going again. I couldn't stop, though: Eric was behind me shouting, 'come on, let's get our home-made tractor to the finish line!'"
Still there were challenges, with the completely unbalance bike careering across the 13 bridges the duo had to traverse once they arrived in Venice itself.
"The front wheel skidded because all the weight was at the back," Zanardi explained, "but we knew that the goal was close and we couldn't give up.
"After the last bridge I stopped to wait for the guy who was supposed to be coming back with Eric's front wheel, so we could reattach it and have him push himself over the line.
"But he never came, so I decided to pull Eric up to a centimetre from the line, then I got out of my handbike, detached his, and pushed him over because I wanted him to be first to pass the finish line.
"It's been tough but an incredible feeling. I could not give up because Eric believed we would get there from the first metre to the very last."
