Heat oven to 350F. Grease a 9x5 inch loaf pan and line with parchment, leaving an overhang for easy removal. Grate zucchini on the large holes of a box grater, then wrap in a clean kitchen towel and squeeze firmly to remove excess moisture. You want about 1 cup packed, dry zucchini. Toss blueberries with 1 teaspoon flour in a small bowl and set aside.

In a large bowl, whisk together flour, baking powder, baking soda, and salt. Add sugar and lemon zest, then use your fingertips to rub the zest into the sugar until fragrant and pale yellow. This releases the lemon oils and perfumes the whole cake.

In a medium bowl, whisk melted butter, eggs, yogurt, lemon juice, and vanilla until smooth. The mixture will look slightly curdled at first but will come together.

Pour wet ingredients into the flour mixture and fold with a spatula until just combined with a few streaks of flour remaining. Add the squeezed zucchini and fold gently, then add floured blueberries and fold until evenly distributed. Do not overmix - the batter should be thick and slightly lumpy.

Scrape batter into prepared pan and smooth the top. Bake 45-55 minutes, until the top is golden and a toothpick inserted in the center comes out clean or with a few moist crumbs. The cake will pull slightly away from the pan edges. Cool in pan 15 minutes, then lift out using parchment and cool completely on a wire rack.

Whisk powdered sugar and lemon juice until pourable but thick, adding more juice by the teaspoon if needed. Drizzle over completely cooled cake. Let glaze set 15 minutes before slicing.