But three years after his diagnosis, he's no longer tuned out to the world around him. He attends kindergarten. Dances with his big sister, Makenna. Giggles with friends.
"I have my son back," says his mother, Deanna Ballard.
One of the keys to his turnaround, she believes, is a series of educational DVDs she and a friend created for Zachary out of frustration and desperation. Ballard's My World Learning videos have captured the attention of parents around the country and earned praise from specialists in learning delays.
Ballard, who has a background in psychology, stresses the DVDs are not a "cure" for autism. Ballard and her husband, Rob, attribute Zachary's progress to a wide range of things, including countless hours of behavioral therapy, medical treatments and changes in his diet. But the videos, she says, have played an important role in bringing "the joy of childhood" back to Zachary and helped put him on a path toward a normal life.