Heat a large pot over medium heat. Add olive oil and onion, and sauté until the onion softens and becomes translucent, about 5 minutes.
Add garlic, zucchini, potatoes, fresh herbs and a pinch of salt, stir well. Cook until vegetables start to soften and brown, about 5 minutes. If needed, add a splash of water to help prevent the vegetables from sticking to the bottom of the pot.
Next add vegetable broth, stir well. Raise heat and bring soup to a boil. Once the soup has reached boiling point, reduce heat to a simmer and cook until vegetables are soft, around 20 minutes. Stir through oat milk and nutritional yeast. Set soup aside to cool for at least 10 minutes.
While soup is cooling, prepare zucchini slices for the garnish. Heat a skillet over medium, add olive oil and zucchini slices. Cook until zucchini is soft and golden brown on both sides, around 8 to 10 minutes. Set aside.
Once the soup has cooled slightly, using an immersion blender or counter top blender, carefully blend until the soup is smooth and creamy. If you used a counter top blender, return soup to pot. Taste the soup and adjust seasoning as needed. If necessary, reheat the soup.
Ladle soup into bowls and top with pan-fried zucchini slices and fresh herbs.
Nutritional information is to be used as a guide only as calories and nutrition vary between products and brands worldwide.