To prepare crust, combine cooked rice, 1/4 cup sugar, beaten egg whites and cinnamon.
Spray a 9-inch pie pan with non-stick vegetable spray.
Spread the rice mixture evenly over bottom and sides of pan, pressing lightly with fingertips or the back of a spoon to shape into a crust.
Bake at 350F for 10 minutes; cool to room temperature.
For the filling, put the rhubarb in a saucepan with the zucchini, cherries, sugar, honey and 2 tablespoons orange juice and cinnamon; simmer over low heat for 15 to 20 minutes or until rhubarb and zucchini are tender; taste for tartness and add more honey or sugar as needed.
Place the remaining 3 tablespoons of orange juice in a bowl and sprinkle the gelatin powder over juice; let soak a few minutes to soften.
Turn the cooked rhubarb mixture into food processor (or use an immersion blender) and puree; return the pureed mixture to the saucepan and bring back to a simmer.
Pour gelatin into the hot puree and stir until the gelatin is completely dissolved, let cool to room temperature and then turn out into the crust.