Mix the zucchini and garlic pieces with one tablespoon of oil to coat and bake in the oven until golden brown (about 15-25 minutes). Stir halfway through.
Peel and wash the potatoes, cut them into small pieces, and boil them with one liter of water at medium temperature with a lid on (about 15-20 minutes).
Set aside a few roasted zucchini pieces for garnish. Transfer the rest together with the garlic to the pot of potatoes and puree with the water (using an immersion blender is recommended; puree coarsely for a chunky soup).
Season with salt and pepper to taste.
Divide the soup between four plates or bowls, top each with reserved zucchini pieces, and drizzle with one tablespoon of rapeseed oil. Serve hot.