Stir in cream, lemon juice, salt, and pepper, then cool to room temperature, uncovered
Chill soup, covered, until cold, at least 4 hours and up to 2 days
While soup is chilling, cook julienned zucchini in boiling salted water until crisp-tender, about 30 seconds, then drain and transfer to a bowl of ice and cold water
Drain and pat dry with paper towels
Season with salt and pepper and chill, covered
Before serving soup, cut each scallop horizontally into 3 rounds and pat dry
Heat oil in a large nonstick skillet over high heat until hot but not smoking, then sear scallops until golden brown, 20 to 30 seconds on each side, and season with salt
Serve soup with zucchini mounded in center, topped with scallop rounds