1. Prepare the broth and preheat the oven to 210 degrees Celsius. Crush or finely chop the garlic and thinly slice the onion. Peel the sweet potatoes and regular potatoes and cut them into 2 cm pieces. Cut the zucchini into 1/2 cm pieces.
2. Heat half of the olive oil in a soup pot and sauté the onion and garlic over medium-high heat for 1 minute. Add the cumin and paprika halfway through cooking, then continue cooking. Add the broth, potatoes, and sweet potatoes, bring to a boil, then reduce the heat to medium-low. Cover and simmer for 15 minutes.
3. Meanwhile, roughly chop the coriander and dice the feta. Crush the cashews. Bake the white ciabatta for 6 to 8 minutes.
4. Heat the remaining olive oil in a pan and cook the zucchini cubes over medium-high heat for 6 to 8 minutes or until golden brown. Season with salt and pepper.
5. Blend the soup using an immersion blender and add water if needed to thin it out. Stir in the black balsamic vinegar, then season with salt and pepper.
6. Serve the soup in bowls, then garnish with feta, cashews, zucchini, and coriander. Serve with the ciabatta.