Meanwhile, with the motor running, drop garlic through the feed tube of a food processor. Process until finely chopped. Stop and add scallions, parsley, lemon zest, lemon juice, capers and mustard. Pulse until the scallions are finely chopped. Add eggs; pulse until chopped. Add 4 tablespoons oil, 1/2 teaspoon salt and 1/4 teaspoon pepper; pulse to combine.