How to Make It
Preheat the oven to 350°. Spread the hazelnuts in a pie plate and toast for 8 minutes, until fragrant and light golden. Let cool, then coarsely chop the nuts.
Meanwhile, in a large skillet, cook the bacon over moderate heat until browned on both sides, about 8 minutes. Drain the bacon on paper towels and crumble into 1/2-inch pieces. Discard the bacon drippings and wipe out the skillet.
In a medium saucepan of boiling salted water, blanch the asparagus until bright green, about 1 minute. Drain, rinse the asparagus under cold water and pat dry.
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.