Heat vegetable oil in a large wok or heavy skillet over medium-high heat until shimmering.
Add the sliced chicken breast in a single layer and sear until golden brown and cooked through, approximately 5-6 minutes. Remove chicken and set aside.
In the same wok, add the minced garlic and ginger, sautéing for 30 seconds until fragrant.
Add the zucchini and bell peppers to the wok. Stir-fry for 3-4 minutes until the vegetables are tender-crisp.
Return the cooked chicken to the wok.
Pour the ponzu sauce and sesame oil over the mixture. Toss continuously for 1-2 minutes until the sauce coats all ingredients evenly.
Remove from heat and garnish with sliced green onions and toasted sesame seeds. Serve immediately.