In a pan, fry breadcrumbs in 2 tablespoons hot oil until golden-brown. Transfer to a bowl. Rinse, trim and finely chop summer squash. Peel and finely chop garlic. Drain and finely chop capers and sun-dried tomatoes. Peel and finely chop onion. Drain sardines and flake into pieces with a fork. Place sardines in the bowl with breadcrumbs. Mix in onion, capers, sun-dried tomatoes, garlic, summer squash, remaining oil, parsley, and lemon juice. Season with salt and pepper. Chill about 20 minutes before serving.