Preheat oven to 375°F. Grease 1 large or 2 small loaf pans.
In a large bowl, cream together the cream cheese and butter until smooth. Add sugar, eggs, and lemon zest and beat until light and fluffy.
In a separate bowl, whisk together flour, baking powder, salt, and cinnamon (if using).
Gradually mix the dry ingredients into the wet ingredients, alternating with milk. Stir just until combined. Fold in the peaches.
Pour batter into prepared loaf pan(s) and bake for 50–55 minutes for a large loaf or 45–50 minutes for two smaller loaves, until a toothpick comes out clean.
Let the loaf cool before slicing and serving.
Notes
If using fresh peaches instead of canned, peel and dice about 2 medium peaches. You may want to lightly toss them in flour to prevent sinking.