If you wish, bulk up this salad with protein such as hard-boiled eggs or a fried eggs on top. Tip: When frying eggs, some of the olive oil over the whites to let them crisp up, then set for one or two minutes.
Another idea is to add sautéed pancetta (a type of ham). Regular mature spinach leaves (not baby) will hold up to the heat. You could also substitute kale.
Combine the olive oil, lemon juice, vinegar, garlic, salt, sugar, and crushed pepper flakes in a jar with a lid and shake well to combine.
Slice the roasted red bell peppers into thin strips. Dry the spinach thoroughly and tear into bite-size pieces. In a large salad bowl, combine the roasted red peppers, spinach, zucchini, and scallions.
Before serving, toss with dressing.