Cut chicken into 1-inch pieces.
Whisk eggs in a bowl. Mix cornstarch, flour, salt, and pepper in another bowl.
Dip chicken in egg, then coat in cornstarch mixture.
Heat oil to 350°F in a large pot.
Fry chicken in batches for 4-5 minutes until golden.
For sauce: Combine orange juice, brown sugar, vinegar, soy sauce, zest, garlic, and ginger in a pan.
Bring to simmer. Mix cornstarch with water and add to sauce.
Cook until thickened, about 3-5 minutes.
Toss fried chicken in sauce.
Garnish with green onions, sesame seeds, and orange zest.