Place large pot on stovetop over medium heat. Add 3 tablespoons olive oil to pot and continue heating until oil is hot and shimmery.
When oil is hot, add ¼ cup sliced green onions, 2 tablespoons minced fresh garlic, 1 anchovy fillet, and ¼ teaspoon red pepper flakes. Stir to incorporate, then sauté ingredients until green onions begin to wilt, approximately 2 to 3 minutes.
Add ⅓ cup dry white wine to pot and stir to incorporate. Increase heat under pot to high. Bring liquid to boil and let boil 2 minutes or until liquid is reduced by approximately 33%.
Add 1 14-ounce can crushed tomatoes, 1 cup clam juice, ½ teaspoon dried oregano, and ¾ cup water to pot. Stir to incorporate.
Bring mixture to simmer, then reduce heat to medium and simmer until color deepens slightly, approximately 10 minutes. Stir occasionally.
Once color has deepened, add ¾ teaspoon salt, 1 ½ pounds white fish, and 1 pound clams to pot and stir to incorporate.
Increase heat under pot to high. Cover pot and cook until clams open and fish flakes easily with fork, approximately 5 minutes.
Add 1 tablespoon chopped fresh parsley, 1 tablespoon chopped fresh basil, 1 tablespoon fresh lemon juice, and freshly cracked black pepper to taste. Stir to incorporate.
Ladle stew into serving bowls. Drizzle additional olive oil on top and serve with lemon zest and crusty bread.