In a large bowl, combine chicken, cornstarch, salt, and pepper together, tossing until chicken is evenly coated in cornstarch.
Heat a large nonstick skillet over medium-high heat, add vegetable oil, and swirl to coat bottom. Begin adding chicken to skillet, shaking off excess cornstarch back into bowl. Cook chicken until golden brown on all sides, turning occasionally. Transfer chicken to a clean plate and set aside for a moment.
In a medium bowl, whisk sweet chili sauce, honey, rice vinegar, soy sauce, garlic, and ginger. Set aside for a moment.
Add zucchini and onion to same skillet you used for the chicken and sauté in pan drippings over medium-high heat until crisp-tender, about 3-5 minutes. Reduce heat to medium.
Pour sauce into skillet over vegetables and bring to a simmer over medium heat. Add mango and chicken and cook 3-5 minutes until heated through and sauce is thickened and clinging to chicken.
Remove mango chicken from heat and season sauce with salt and pepper to taste if needed. Serve warm over hot rice with green onions garnished on top. Enjoy!