Whisk together orange juice, soy sauce, sugar, rice vinegar, ginger, garlic, and orange zest in a small bowl until the sugar dissolves.
Toss the chicken pieces with cornstarch until evenly coated and shake off any excess.
Heat vegetable oil in a large skillet over medium-high heat and fry the chicken in batches for 4 to 5 minutes per side until golden and crispy, reaching 165°F / 74°C at the thickest part.
Remove the chicken to a plate and pour the orange sauce into the same skillet, simmering for 2 to 3 minutes until thickened and glossy.
Return the chicken to the skillet and toss quickly to coat, then remove from heat immediately to keep the coating crisp.
Serve hot over steamed rice or as desired.