Preheat oven to 430°F or 220°C.
Grate zucchini, add to a clean kitchen towel and squeeze out as much liquid as possible. Combine all crust ingredients and mix well by hand.
Line a baking sheet with parchment paper. Sprinkle with a little flour. Spread the zucchini crust mixture evenly with a fork or spoon, about ½ inch thick. Make smaller circles or go for a big pizza in the shape of your baking sheet to share. If the crust feels to wet, add a little bit more flour (or panko/breadcrumbs works too) to the mix.
Pre-cook crust for 10 minutes or until lightly browned.
Top with sauce, then mozzarella cheese, followed by onion and bell pepper.
Grill for 10 minutes in the oven, or until cheese has melted and browned.
Top with arugula and serve.