Bring a large, generously-salted pot of water to a boil. Add the macaroni and cook according to package instructions. Drain in a colander and run under cold water until the macaroni is completely cooled. Shake the colander well to get rid of excess water. Transfer the macaroni to a large bowl.
While the macaroni is cooking, make the dressing. Combine the yogurt, feta, olive oil, lemon zest, lemon juice, 2 teaspoons salt, pepper and garlic in a food processor. Blend until well mixed. Scrape the dressing into the bowl with the macaroni. Add the tomatoes, radishes, carrots, scallions, cucumber and dill to the bowl and toss well. Check for seasoning. Add more salt and pepper if desired.