In a wide, shallow dish, mix zest and sugar together with your fingers. Wet the rim of 8 cocktail glasses with a wet paper towel, and then dredge in clementine sugar to coat. In a large pitcher, use a wooden spoon to muddle cranberry juice, cranberries. Fill pitcher with ice cubes. Top off with clementine juice, and prosecco. Stir vigorously; pour into glasses; garnish with clementine twists and serve.