Brown the ground beef in a large skillet over medium-high heat with ½ tablespoon of olive oil. Break apart, fully cook, and push to one side of the pan.
Add the remaining olive oil and zucchini. Cook until the zucchini starts to pick up color and soften, about 3 minutes.
Add the mushrooms and stir everything together before adding the Teriyaki sauce. Cook until the sauce is evenly distributed and sticking to the stir fry, about 1-2 minutes.
Serve the ground beef over rice with the sauce. Garnish with scallions and sesame seeds, if desired.
