Preheat oven to 350 degrees. Spread bread evenly on a large baking sheet and toast for 10-15 minutes until crispy. Remove from oven and set aside to cool.
While bread is toasting, use a mandolin to slice the zucchini, cucumbers and red onion into paper thin rounds. Toss with 1/2 teaspoon salt and set in a colander to drain for 15 minutes. Briefly rinse.
Toss bread, vegetables, cannellini beans, and basil in a large bowl. Whisk together olive oil, vinegar and garlic and season with salt and black pepper. Pour over the panzanella and let sit 10 minutes before serving.
