Drain tofu. Marinade in soy sauce and fresh ginger for at least an hour. Drain excess soy sauce and toss in cornstarch.
Heat sunflower or vegetable oil in a wok or large skillet over medium heat. Add tofu and cook on each side until golden brown and crispy. Remove from the pan and set aside.
Heat sesame oil in the wok or large skillet over medium-high heat until smoking. Toss in broccoli and cook until crisp-tender, about 1 to 2 minutes. Remove from pan, set aside and do same with pepper, carrots, and zucchini.
Turn heat down to medium and add all the sauce ingredients in the wok or large skillet, except the cornstarch. Bring to a gentle boil. thickness, remove from heat.
Mix cornstarch with cold water. Slowly pour into the sauce, stirring continuously. When sauce has thickened to desired
Add reserved veggies and crispy tofu back to the pan along with the green onions.