Whisk the Marinade: In a large mixing bowl, combine the olive oil, lemon juice, lemon zest, minced garlic, za'atar, cumin, salt, and pepper. Whisk until well-emulsified.
Combine: Add the rinsed chickpeas, butter beans, sliced red onion, cucumber, tomatoes, and olives to the bowl.
Toss with Herbs: Add the fresh parsley and mint. Toss the salad thoroughly until all ingredients are glossy and evenly coated with the dressing.
Marinate: Cover and refrigerate for at least 30 minutes (up to overnight) to allow the beans to absorb the dressing.
Serve: Give it one final toss. Taste and add more lemon or salt if needed. Top with crumbled feta or an extra sprinkle of za'atar if desired.
