Heat the olive oil in a large pan on medium-high heat. Once hot, add the onion and cook for 2 minutes. Next, turn the heat down to medium and add the garlic, some salt and pepper. Cook for an additional minute. Next, add the leek and celery, cover with a lid and cook for 5 minutes. Then, turn heat down to medium-low, add the zucchinis, cover and cook for an additional 5 minutes. Add the water and vegetable bouillon and turn up heat until contents come to a boil. Once boiling, turn down to a simmer and simmer for 5 minutes.