In a large bowl, whisk together the yogurt, cilantro, red onion, lime zest, lime juice and vinegar. Season with salt. Cover and refrigerate until ready to use.
Preheat a grill to high. In a large bowl, whisk together the EVOO and curry powder. Add the zucchini and bell peppers and toss to coat. Season with salt and toss again.
Grill the zucchini and peppers, flipping halfway through, until just charred but still firm, about 3 minutes per side. Transfer the grilled vegetables to a large baking sheet and let cool completely.
Cut the zucchini crosswise into 1-inch-thick pieces; cut the peppers into 1/4-inch-wide strips. Return the vegetables to the baking sheet; toss in the arugula and enough dressing to lightly coat. Season with salt. Transfer the salad to a platter and serve immediately with the remaining dressing on the side.