Toss chicken pieces with cornstarch until lightly coated.
Heat oil in a large skillet over medium-high heat. Cook chicken in batches until golden and cooked through. Remove and set aside.
In the same skillet, add garlic and ginger. Cook for 20–30 seconds until fragrant.
Stir in orange juice, orange zest, soy sauce, and sugar. Bring to a gentle simmer.
Add cornstarch slurry and cook until the sauce thickens and becomes glossy.
Return chicken to the skillet and toss until evenly coated in the orange sauce.
Remove from heat and serve immediately.