Preheat the oven to 350°F, and line a loaf pan with parchment paper overhanging on the sides.
In a large bowl, combine the flour, cinnamon, baking soda, baking powder and salt. Whisk together until well combined; set aside.
In another large bowl, whisk together the wet ingredients including the eggs, sugar, Greek yogurt, and mashed banana until well combined. Gently fold in the diced strawberries and walnuts.
Pour the dry ingredients into the wet ingredients and stir gently. Do not overmix.
Transfer the batter into the prepared loaf pan, spreading it out evenly, and bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to get too brown, cover it with a sheet of aluminum foil after 35 minutes.
Remove from oven, and let it cool for about 10 minutes before transferring to a wire rack to cool completely. Store in an airtight container at room temperature for up to 5 days, or freeze for up to 3 months.