Cut chicken into cubes.
Dredge each piece in cornstarch and shake off excess.
Heat oil in skillet and pan fry chicken pieces until golden on all sides.
Remove to a plate lined with paper towels to remove excess oil.
For the sauce, in a pot combine the water, orange juice, lemon juice, rice vinegar, and Tamari. Stir to combine on medium. Add the zest, brown sugar, garlic and scallions. (reserve some of the scallions for when you plate the chicken) Bring to a boil.
Stir the cornstarch and water until smooth. Add this into the boiling sauce and cook until thick which happens pretty quickly. Return chicken to skillet to coat with sauce.