Combine the vinegar, lemon juice, honey, mustard, 1 ½ Tbsp fresh dill and salt and pepper to taste in a blender. Blend until smooth. With the motor running, slowly add ¼ cup olive oil and blend until emulsified.
Brush zucchini with the remaining oil and season with salt and pepper. Grill turning, until lightly golden brown on all sides, about 6 – 8 minutes.
Remove from the grill and cut each quarter in half crosswise. Place on a platter and immediately drizzle with the vinaigrette. Garnish with the remaining dill.