Tart: Sprinkle zucchini with salt in a colander; let stand 15 minutes. Rinse with cold water; pat dry with paper towel. Toss zucchini, mushrooms, charcuterie slices, oil and lemon zest in a bowl. Unroll pastry dough onto 1/2 sheet tray; leaving a 3/4-inch border, lightly score a frame around the pastry. Whisk 1 egg, cheeses and pepper in a bowl; spread ricotta mixture over pastry within the frame; top with mushroom mixture and refrigerate 30 minutes.

Brush remaining egg over pastry around filling. Bake tart at 400°F until golden brown and flaky, about 30 minutes. Cool; cut into 4 pieces. Wrap tart on sheet tray with plastic wrap; refrigerate up to 3 days.

For serving, plate tart at room temperature garnished with thyme sprigs.