Preheat oven to 325 degrees. Spray an 8 X 4-inch loaf pan with nonstick cooking spray.
Make the Bread; In a large mixing bowl, mix together sugar, vegetable oil, egg, lemon extract and lemon zest. Fold in zucchini. Set aside.
In another mixing bowl, whisk together flour, salt, baking soda, and baking powder. Add the flour mixture to zucchini mixture in 2 additions, mixing just until the flour is moistened. Do NOT overmix.
Pour batter into prepared pan. Bake in preheated oven for 45 minutes or until a toothpick inserted into the center comes out with just a few moist crumbs.
Make the Lemon Syrup while bread is baking. In a small saucepan, cook the sugar and lemon juice over low heat until the sugar dissolves. When the cake comes out of the oven, generously brush the top with the lemon syrup. Allow the cake to cool in its pans for 10 minutes, glazing the tops a few more times while it cools in the pan. Remove the cake from the loaf pan and set it on a wire rack, set over the baking tray or a piece of aluminum foil, to catch drips. Brush the sides and top of the cake with the remaining syrup, allowing a couple of minutes between brushings, to allow syrup to absorb into the cake until the syrup is gone. Cool the bread completely.
Make the Lemon Glaze; In a small mixing bowl, mix together powdered sugar and 2 tablespoons lemon juice until smooth. Add more lemon juice, a teaspoon or so at a time, as needed to reach a thick but pourable consistency. Pour the glaze over the bread. Let it sit out at room temperature until the glaze has dried well.