Preheat broiler and set oven rack 6 incehs from heat source. Grease baking sheet. Cut zucchini in half long ways and scoop out the seeds and pulp, leaving a thich shell of flesh. Brush both halves of the zucchini with about 1 tbs of olive oil and place them cut side down onto the prepared baking sheet. Bake until the zucchini are hot and beginning to release beads of moisture approx 5-10 min. Remove the zucchini from the oven. Reduce the oven heat to 450. Heat 2 tbs of olive oil in a skillet over medium-low heat, cook garlic and shallot until translucent, about 5 min. Remove from the heat and let cool. Place 1 tbs of olive oil, the shrimp, diced tomato, mushroom, parm cheese, basil, and the cooked garlic and shallot into a bowl. Season to taste with pepper, salt, and garlic powder. Stuff the mixture into the zucchini halves and sprinkle each zucchini with about 2 tbs of parm cheese. Bake the zucchini in hte preheated oven until the cheese is browned and filling is cooked through and hot...about min.