Heat broiler. If using a broiler-proof rimmed baking sheet, set rack 4 inches from heat; if using a broiler pan, set rack so that top of pan is 4 inches from heat. On sheet (or pan), toss zucchini and tomatoes with dill, 1 tablespoon oil, 1 1/2 teaspoons salt, and 1/4 teaspoon pepper. Broil until tender and slightly charred, 20 to 25 minutes; transfer to a plate to cool. Wipe sheet (or pan) clean with a paper towel.
Place split pitas on sheet (or pan); broil until lightly browned, 1 to 3 minutes per side (watch closely). Cool, then break into small pieces.
In a small jar or bowl, combine vinegar and remaining 2 tablespoons oil with 1/2 teaspoon salt and 1/8 teaspoon pepper; shake or whisk until combined and thickened.
Divide lettuce, zucchini mixture, pita pieces, feta, and olives among serving plates; drizzle with dressing as desired.
Romaine-lettuce hearts (also called hearts of romaine) are often sold in packages of three in the produce section.