Spring Garden Frittata

INGREDIENTS

• 6 eggs, beaten
• 1 Tbs. lemon zest
• 1/2 cup grated Parmigiano-Reggiano cheese
• 1/3 lb. fontina cheese, cut into 1/4-inch cubes
• 2 Tbs. finely chopped fresh flat-leaf parsley
• 3 Tbs. finely chopped fresh chives
• 1 1/2 tsp. kosher salt, plus more, to taste
• 1/4 tsp. freshly ground pepper, plus more, to taste
• 7 tsp. olive oil
• 3/4 cup diced yellow onion
• 1 Tbs. minced garlic
• 1 1/2 lb. zucchini, cut lengthwise into ribbons 1/8 inch thick
• 1 cup peas