In a large mixing bowl, combine the ground chicken, breadcrumbs, egg, minced garlic, red onion, fresh parsley, chopped dill, lemon zest, salt, and pepper. Gently mix until just combined.

Shape the mixture into 1.5-inch meatballs, rolling them gently. Arrange on a parchment-lined baking sheet.

Preheat oven to 400°F (200°C). Drizzle meatballs with olive oil and bake for about 18–20 minutes or until cooked through.

While baking, prepare tzatziki by combining Greek yogurt, grated cucumber, minced garlic, lemon juice, olive oil, chopped dill, and salt. Mix until smooth.

Once meatballs are done, let them rest, then serve warm with tzatziki.