Add saffron to 1 cup boiling water; cover and let stand while you prepare remaining ingredients.
Heat 2 tablespoons oil in a large sauté pan, large wide saucepan or deep skillet over medium-high heat. Add shrimp, scallops, salt and pepper, and sauté about 2 minutes, tossing often. Remove with a slotted spoon. Add zucchini, salt and pepper to pan and sauté about 2 minutes. Remove with slotted spoon.
Add 1 tablespoon oil to pan. Add onion and cook over medium heat about 5 minutes or until soft but not brown. Add garlic and rice and cook over low heat, stirring, about 3 minutes or until grains begin to turn white.
Pour saffron in its liquid and remaining 11/2 cups boiling water over rice and stir once. Add thyme, salt and pepper. Bring to a boil over high heat. Reduce heat to low, cover tightly and simmer, without stirring, for 15 minutes. Scatter shrimp, scallops, zucchini and peas over top. Cover and simmer for 3 minutes or until rice is tender and liquid is absorbed. Discard thyme sprig.
Fluff rice lightly with a large fork, and gently transfer to a bowl. Add remaining 1 or 2 tablespoons olive oil. Cool to room temperature. With a fork, gently stir in peppers, tomatoes and parsley. Add lemon juice. Taste and adjust seasoning.