Denny abides by the custody arrangement and takes Zoë to museums, zoos, and the aquarium, and sometimes he takes her to the go-karts. Enzo says that she was just big enough to fit the first time he took her, and she knew how to drive immediately with no fear.
Consider here the previous discussion about a child potentially possessing Luigi Chinetti's soul. Zoë at a young age is easily accomplishing something that's difficult, as if her soul already knew how.
One day at the karts, the teen on duty asks Denny if he's going to take Zoë to Spanaway, an outdoor go-kart course, telling Denny that Zoë could kick his ass. Denny laughs, and the worker boy challenges Denny, telling him that if Zoë wins, Denny pays, and if Denny wins, he rides for free. Denny accepts. As the race begins, he stays behind Zoë, and after a few laps, he tries to pass her. She blocks him, again and again, and wins the race. Enzo is so happy that he doesn't mind sitting in the car while Zoë and Denny get fries and milkshakes after.
There's no question in Denny's mind that he can easily beat his single-digit aged daughter at something that he's been doing professionally for years. However, with Zoë's win and strong intuition regarding how to drive and win, the reader is again asked to consider Enzo’s ideas of reincarnation, and whether a driver’s soul currently resides in Zoë.
Enzo notes that Denny has a secret. He says that while Trish and Maxwell may restrict Denny's access to Zoë, when he does see her, he gets all the energy he needs to maintain focus for the fight ahead.
Denny's love for Zoë is what keeps him going through his battle with Trish and Maxwell. His love for her is his primary motivator.