Preheat the oven to 350°F.
In a large bowl, beat the butter, oil, sugar and lemon zest for 2-3 minutes, until pale yellow and fluffy. Add the eggs one at a time, beating after each addition.
Stir the lemon juice into the milk and set aside for a few minutes to thicken. In a small bowl, stir together the flour, baking powder, baking soda and salt.
Add about a third of the flour mixture, beating on low speed just until combined. Add half the milk in the same manner, then another third of the flour, the rest of the milk and the rest of the flour. Stir in the chopped lemon.
Divide the batter between two 8”x4” loaf pans that have been sprayed with nonstick spray. Bake for 50-60 minutes, until golden and tops are springy to the touch. Let cool for about 10 minutes before turning out onto a wire rack to cool completely.