Slice zucchinis. Sheets should be 3-5 millimeters thick. Peel and chop the garlic clove.
Heat up your griddle pan gradually. Start at medium temperature and increase intensity progressively until pan reaches the desired temperature.
Use a kitchen brush to uniformly paint zucchinis with olive oil. Grill them at high temperature during 5 minutes. Turn them upside down, add garlic, salt and pepper. Grill during 5 minutes. Add rosemary and serve.