Heat oil in a large saucepan over medium heat. Add onion and celery; cook and stir until onion is translucent, about 5 minutes. Stir salmon, reserved juice, chicken broth, potatoes, carrots, and salt into the saucepan. Bring to a simmer, stirring frequently, about 10 minutes. Cover and simmer, about 10 minutes more. Stir zucchini into the saucepan; simmer for 5 minutes. Pour in cream-style corn and milk; cook until heated through, 5 to 10 minutes.