Quarter the potatoes and place in a large saucepan. Cover the potatoes with water. Bring to a boil. Reduce heat and simmer, uncovered, for about 10 minutes or until potatoes are tender. Drain. Return the potatoes to the saucepan. Using a potato masher, mash the potatoes. Add the butter and milk, continue to mash until potatoes are somewhat smooth. Add the parsley, lemon zest and garlic to the potatoes and stir to blend. Adjust seasonings to taste with salt and freshly ground black pepper.