If using fresh corn, remove husks and silk from ears. Bring a large pot of water to a boil. Add the corn and cook for 3 minutes. Remove the corn from the water, draining well, and allow to cool to room temperature.

Heat one tablespoon of oil in a large skillet over medium high heat. Add the zucchini matchsticks. Season with 1/4 teaspoon salt and freshly ground pepper to taste. Cook, tossing the zucchini sticks frequently, until they are lightly browned, about 3-5 minutes.

Transfer the zucchini to a large bowl.

Reduce the heat under the skillet to low, add the second tablespoon of oil and the diced onion. Sprinkle 1/4 teaspoon of salt over onion and stir well. Cover skillet and allow onions to slowly cook for about 10 minutes, stirring occasionally. They will soften but not brown. Remove the skillet cover.

Add the minced garlic to the skillet and cook for one minute.

Add the white wine vinegar and oregano to the onion mixture. Allow to simmer for two minutes, stirring now and then. Pour the onion mixture over the zucchini and toss to combine. Mix in the chopped mint. Allow the mixture to cool to room temperature.

Add the corn to the zucchini mixture. Taste and add more vinegar, if desired. Season with additional salt and pepper, if needed.

Refrigerate.

Garnish with mint leaves to serve.