You can grill the zucchini a day ahead, then about an hour before guests arrive, puree the zukes and the other dip ingredients in the food processer.
In a large bowl, toss the zucchini and oil; season with salt and pepper. Heat a grill over medium. Grill the zucchini until tender and charred in spots, turning often, 5 to 10 minutes. Let cool. Cover and refrigerate for up to 1 day.
In a food processor, puree the zucchini, tahini, lemon zest and juice, and garlic; season. Transfer the dip to a bowl. Top with the mint and pine nuts. Serve with chips.