In a medium bowl whisk the oil, oregano, chili powder, cumin, salt, and pepper. Add the shrimp and toss to coat.
In another medium bowl whisk the oil, oregano, salt, and pepper. Add the zucchini and toss to coat.
Prepare the grill for direct cooking over medium heat (350° to 450°F) on one side of the grill and high heat (450° to 550°F) on the other side.
Place the apricot halves on a plate and brush with the oil. In a small bowl whisk the honey, lime juice, and serrano chile. Set aside.
Brush the cooking grates clean. Grill the apricot halves over direct medium heat, with the lid closed, until slightly softened and grill marks appear, 6 to 9 minutes (depending on the ripeness of the fruit), turning once or twice. Transfer the apricots to a cutting board. Let cool slightly, then dice. Add the apricots to the honey and lime juice mixture and stir in the cilantro. Toss to combine. Season with the salt and pepper. Taste and add more honey, ½ teaspoon at a time, if desired.
Place a perforated vegetable basket over direct medium heat and preheat for about 5 minutes. Spread the zucchini in the vegetable basket and cook, with the lid closed, until just tender, 4 to 6 minutes, turning once or twice. Transfer the zucchini to a bowl and tent with foil to keep warm.
Return the vegetable basket to the grill over direct high heat, and preheat for 2 to 3 minutes. Add the shrimp and grill, with the lid closed, until they are firm to the touch and just turning opaque in the center, 4 to 6 minutes, stirring once or twice. Transfer the shrimp to another bowl.
Grill the tortillas over direct medium heat until slightly charred on both sides but still soft, 1 to 2 minutes, turning once.
Place one tortilla on each of four plates and divide the zucchini slices among the tortillas. Top the zucchini with the shrimp, and then the salsa, dividing evenly. Sprinkle the feta over each tostada and serve immediately.