Step 1Place the ground pork and beef in a food processor and pulse several times. Transfer to a large bowl. Trim the ends of the zucchini and chop finely. Add to the bowl.
Step 2Finely grind the peppercorns and cumin seeds in a spice grinder or mortar and pestle and add to the meat. Add the oregano, eggs, onion and salt and gently use your hands or a spatula to thoroughly combine all the ingredients.
Step 3Gently form the mixture into 1 1/2 -inch meatballs. Place on a baking sheet and refrigerate while making the sauce.
Step 1Bring a large pot of water to a boil. Core the tomatoes and place them in the boiling water. Reduce the heat and simmer for 5 minutes. Drain the tomatoes and cool for a few minutes.
Step 2Process the tomatoes and chipotle chiles in a blender or food processor until smooth.
Step 3Heat the oil in a large skillet and add the tomato sauce. When it comes to a boil, reduce the heat and simmer for 5 minutes. Add the chicken broth. When the sauce comes back to a simmer, add the meatballs.
Step 4Cover the pan and simmer the meatballs over low heat until they are cooked through, about 50 minutes. Adjust the seasoning by tasting and adding salt just before the end of the cooking time. This dish can be prepared a day ahead or can be frozen and reheated.