Slice zucchini into 5mm pieces. Remove seeds and stem from red bell pepper, cut into strips and then diagonally into thirds. Trim shimeji mushrooms and separate them by hand. Slice garlic and remove its core.

Cut chicken thigh into bite-sized pieces and season with salt and pepper.

Heat olive oil and garlic in a frying pan until fragrant. Add chicken skin-side down and cook over medium heat until browned. Flip chicken, then add zucchini, red bell pepper, and shimeji mushrooms. Stir until coated with oil.