Heat oil in a wide frying pan over medium-high heat.
Add garlic; cook, stirring, for 2 to 3 minutes.
Add zucchini and cook, stirring often, just until tender-crisp to bite 3 to 5 minutes.
Stir in parsley, onion, oregano, and sugar.
Season to taste with salt and pepper.
Continue to cook, stirring, until zucchini and seasonings are well blended 1 to 2 more minutes.