Zion was diagnosed with sepsis, a life-threatening infection, at the age of two. Doctors had to removed both his hands at the wrist, and his legs below the knee. His kidneys had also failed.
After two years of dialysis, at the age of four, Harvey had a kidney transplant using a kidney donated by his mother.
At the age of eight, he underwent the surgery and two years later with his new hands Harvey can write, feed and dress himself, as well as grip a bat. His brain has accepted the donor hands as his own, doctors said.
"He is able to swing a bat with much more co-ordination, and he can write his name quite clearly," Sandra Amaral, a member of the team treating Harvey at the Children's Hospital of Philadelphia (CHOP) told the BBC.
Although the first ever double-hand transplant was done in 1998, Harvey became the youngest to ever undergo the procedure in 2015.
Double hand transplantation is a complex procedure involving many surgical and non-surgical components. First, the potential recipient must undergo extensive medical screenings and evaluations before surgery.