Cut carrot and zucchini in half lengthwise, then finely slice on the bias. Remove seeds and membranes from pepper and cut into fine julienne.
Heat oil in a hot wok until surface seems to shimmer slightly. Add carrot, tofu, onion and ginger and stir-fry for 1 minute. Add wine or sherry, zucchini, pepper and sugar and stir-fry for 1 minute. Pour in soy sauce, vinegar, oyster sauce and sesame oil and stir-fry for a further minute or until vegetables are just tender. Toss in scallion and sesame seeds, stir-fry for 10 seconds, then remove from heat.