Combine flour, cornstarch, and a pinch of salt in a shallow dish or pie plate. Beat the eggs in a separate shallow dish. Dip the chicken pieces in the egg wash, then the flour mixture. Shake off excess flour and transfer to a plate. Set aside.

Whisk the orange juice, sugar, cornstarch, vinegar, soy sauce, ginger powder, garlic, and red chili flakes together in a medium bowl. Set aside.

Heat 2-3 inches of oil in a heavy-bottomed pot or wok over medium-high heat until it reaches 350 degrees F. Work in batches to cook the chicken, being careful not to crowd the pan which will cause the oil temperature to drop significantly. Cook for 2-3 minutes, turning frequently until brown and crispy on the outside and cooked through. Transfer to a wire cooling rack to drain and repeat with the remaining chicken.

Drain most of the oil from the pan, leaving only about 1 tablespoon in the bottom. Add the garlic and saute for 30 seconds, then pour in the sauce mixture. Heat, stirring frequently, for 5 minutes until thickened. Remove from the heat and stir in the orange zest.