For the zucchini: Preheat a large grill pan over medium-high heat.
Combine all of the zucchini with the oil and salt in a large bowl and toss to coat.
Working in batches, grill the zucchini in a single layer until it starts to soften and grill marks appear on one side, about 4 minutes. Flip and repeat on the other side, about 2 minutes. Transfer to a separate large bowl.
Meanwhile, for the vinaigrette: Combine the lemon zest, lemon juice, shallot, garlic, Dijon, and salt in a medium bowl and whisk together. While whisking, drizzle in the olive oil and sunflower oil. Whisk in the mint and Aleppo pepper.
Add about 1/3 cup of the dressing to the zucchini and gently toss. Transfer to a serving plate.
For serving, sprinkle the zucchini salad with the feta, mint, Aleppo pepper and flaky sea salt.