Preheat the oven to 240°C / 450°F (220°C fan) and position the oven rack near the top.
Trim the ends off the zucchinis. Cut the medium zucchinis into quarters lengthwise. For the large zucchinis, halve them lengthwise, then cut each half into three long wedges, making six pieces per zucchini.
Place all the zucchini pieces on a baking tray. Drizzle with 1 tablespoon of olive oil, then season with salt and pepper. Toss to coat evenly.
Arrange the zucchini in two rows on the tray, placing them close together with the skin side facing down.
Sprinkle the breadcrumbs evenly over the zucchini, followed by the grated parmesan. Drizzle with the remaining 1 tablespoon of olive oil.
Bake for 12 minutes, or until the parmesan turns golden and the zucchini is tender without becoming soggy.
Serve immediately.