Preheat oven to 375 ℉. Line a 9 x 13 pan with parchment.
Filling: Cook zucchini and lemon juice on low heat for 15 - 20 min until tender. Stir in the granulated sugar. Remove from heat. Stir in blueberries and let cool while you make the crust.
Crust: In the bowl of the stand mixer combine flour, brown sugar, oats, baking powder and cinnamon. On low speed add the butter in chunks and let mix until crumbly.
Remove ½ cup of crumb mixture and add to blueberries. Stir in.
Press ⅔ of the remaining mixture into the bottom of the pan.
Spread berry mixture on top.
Crumble the remaining mixture onto the top, pressing it into clumps.
Bake 40 minutes.
Recipe by Chateau Elma at https://www.chateauelma.com/blueberry-zucchini-crumb-bars