When she tried to escape into the back seat, Zabell continued to throw punches, some hitting the young boy.
Zabell had refused to stop driving and had threatened to kill the woman and boy, saying he would not stop hitting the woman until she was dead.
Arriving in Masterton, he had dragged the woman from the car by her hair and had ordered both his partner and the boy to undress because there was blood on their clothing.
Soon after, when his mother tried to intervene, he "back-handed" his mother, hitting her on the jaw.
Zabell also snapped his partner's cellphone in half.
When police later searched Zabell's car they found a baseball bat inside.
Zabell had claimed his partner had endangered their lives by pulling the handbrake on while he was driving and by throwing a towel over his face.
Judge Walsh said Zabell had 29 previous convictions, seven for violent offences.
He said Zabell could well have crashed the car, killing all inside or others the car hit.
"A lot of people are remorseful after violent incidents but remorse can come too late for victims," Judge Walsh said.