Heat oil in 12-inch heavy skillet over moderate heat until hot but not smoking.
Cook scallions, stirring occasionally, until softened, about 3 minutes.
Add garlic and cook stirring for about 1 minute.
Add corn, zucchini, cumin, salt and pepper.
Cook, stirring occasionally until zucchini is tender, about 4-6 minutes.
Stir in cilantro and season with salt and pepper.