Using a sharp vegetable peeler, shave the zucchini lengthwise, creating very thin slices. Discard the first slice that is very dark green skin. Arrange the slices on a platter, overlapping the slices.
In a small jar or bowl, place the lemon juice, olive oil, thyme, salt and pepper. Cover and shake well or whisk to blend. Pour the mixture evenly over the zucchini slices. Allow to sit for at least 15 minutes, or for up to an hour.
Use vegetable peeler to shave thin slices of Parmesan over the zucchini, and serve with baguette slices.