Preheat oven to 400 degrees. Tear off four generous pieces of parchment paper and fold each in half; each should be big enough to fit fish fillet inside with generous room left to fold edges of paper into a packet. Open each folded piece of paper and add a layer of sliced fennel in the middle. Top with a layer of sliced zucchini. Sprinkle veggies with 1/2 tsp. Greek seasoning and 1/4 tsp. dill. Set fish fillet on top of seasoned veggies and sprinkle fish with another 1/2 tsp. Greek seasoning and 1/4 tsp. dill. Drizzle with 1 tsp. olive oil then set 1 Tbsp. butter on top of fillet. Top with a handful of cherry tomatoes and a sprig of reserved fennel fronds. Fold parchment over fish and, starting at one side, roll paper up to seal as well as possible to create a packet. Bake for about 12 to 15 min. depending on size of fillets. Fish should feel slightly firm through the packet at the thickest part of fillet. Let fish rest for a couple of minutes before tearing open packet. Serve topped with fresh fennel fronds, olives, onions, and a lemon wedge.