Season scallops with salt and pepper. Melt 1 tablespoon butter in a large nonstick skillet over medium high heat. Add garlic and cook, stirring, until fragrant, about 30 seconds. Add spinach and stir until wilted. Transfer spinach to a platter and cover loosely with foil to keep warm. Wipe out skillet and return to stove over medium high heat. Add remaining butter. When butter is melted and begins to sizzle, add half of the scallops and cook until browned, about 2 minutes; turn and cook until just opaque, 1-2 minutes longer. Transfer to platter and cover loosely with foil to keep warm. Repeat with remaining scallops. Carefully add lemon juice to the skillet, as butter may splatter. Use a wooden spoon to scrape up any brown bits from the bottom of the pan. Remove from the heat; stir in chives and zest. Pour over scallops and serve.