In the large skillet, heat 1 tablespoon of the olive oil. Add the shallot and cook over moderate heat until fragrant, about 1 minute. Add the zucchini and fennel and cook, stirring occasionally, until just tender, about 5 minutes. Add the asparagus and spinach and cook until the spinach is wilted, about 2 minutes. Season with salt and pepper. Remove the skillet from the heat and stir in the lemon zest and the crumbled bacon. Transfer the vegetables to a platter and drizzle with the remaining 1/2 tablespoon of olive oil. Sprinkle with the hazelnuts and serve.