Heat oil in a large saucepan over medium heat. Add shallot and cook, stirring, until starting to soften, about 2 minutes. Add garlic and cook, stirring, until fragrant, about 30 seconds. Add pasta, broth, water, lemon zest, salt and pepper. Cover and bring to a boil; uncover, reduce heat to medium-high and cook, stirring frequently, for 8 minutes. Add asparagus and cook, stirring, until tender, about 4 minutes. Remove from heat and stir in shrimp and lemon juice. Cover and let stand for a few minutes until the shrimp are heated through. Serve sprinkled with herbs and/or topped with feta, if desired.
