Cut tofu, zucchini, green onion, onion, and shiitake mushrooms into bite-sized pieces.
Pour water into a pot and add kelp to make broth.
Remove the kelp and add the prepared vegetables and shiitake mushrooms. Bring to a boil.
Add doenjang (soybean paste) and minced garlic, stirring to dissolve.
Add tofu and simmer on low heat for another 5 minutes.
Add green onion and bring to a boil once more before finishing.