Preheat your oven to 175°C (350°F). Grease and line two loaf pans with parchment paper to make removing the loaves easier.
In a large bowl, beat the eggs together with the sunflower oil and sugar. Mix well until the sugar starts to dissolve and the mixture looks smooth.
Add the grated zucchini to the wet ingredients. Stir gently to combine. The zucchini will add moisture to the batter.
In a separate bowl, whisk together the all-purpose flour, buckwheat flour, baking soda, baking powder, and cinnamon. Make sure these dry ingredients are evenly mixed.
Slowly add the dry ingredients to the wet mixture. Stir carefully until everything is just combined. Don’t overmix, or the loaves might turn out tough.
Fold in the raisins and chopped walnuts. These will give your loaves a nice crunch and a sweet bite.
Pour the batter evenly into the two prepared loaf pans. Smooth the tops with a spatula.
Bake in the preheated oven for about 55 to 65 minutes. Check doneness by inserting a toothpick in the center; if it comes out clean or with a few crumbs, it’s ready.
Let the loaves cool in the pans for about 10 minutes, then transfer them to a wire rack to cool completely before slicing.