Heat oil and butter in a wide 8- to 9-qt. pot over medium-high heat. Add chorizo, shallots, garlic, Padrón peppers, and lemon zest and cook until shallots soften, 2 to 3 minutes.
Add clams, wine, and 1/2 cup water, then cover and boil, stirring once or twice, until clams open, 8 to 10 minutes. Discard any clams that do not open.
Ladle the dish into bowls and serve with bread.
*Find at well-stocked supermarkets and at spanishtable.com.