Bring large pot of water to boil. Heat olive oil on medium heat in a large skillet. Chop garlic and challot and saute in olive oil, until the onion begins to brown. Drain juice from canned clams, setting aside juice. Add wine, clam juice, red pepper flakes, and juice of 1/2 the lemon to skillet. Raise heat in skillet to medium high, bringing liquid to a boil, then bring heat back to medium-low to simmer.
Add fresh clams, canned clams, zucchini, and tarragon to skillet. Cover skillet and let simmer for 10 minutes or more. Meanwhile, cook linguine al dente, approximately 11 minutes. Drain cooked pasta and place in a serving bowl. Drizzle light olive oil over cooked pasta, sprinkle a little red pepper, and toss. Add skillet mixture to tossed pasta and serve immediately. Slice remaining 1/2 lemon and use as garnish.
Red wines are difficult to pair with clams, but in some cases a cabernet franc will work with this dish. Your safest bet is a dry white wine, such as a pinot gris.