For the pickled peaches: Combine the vinegar, sugar, peppercorns, coriander and bay leaf in a nonreactive saucepan with 1 1/4 cups water. Bring to a boil, stirring to dissolve the sugar. Reduce the heat and simmer for 10 minutes.
Place the peaches in a heatproof, nonreactive bowl or mason jar. Pour the hot pickling liquid over and let cool to room temperature. Refrigerate overnight or up to 48 hours before using.
For the pasta: Cook the pasta in a large pot of boiling salted water, stirring occasionally, until al dente, according to package directions. Drain, reserving the pasta cooking liquid in the pot, and drizzle with the olive oil. Transfer to a bowl, add the asparagus and radishes and toss to combine. Add the herbs, lemon zest and pepper flakes and toss to combine again. Let cool.
Stir in the arugula, 1/4 cup pickled peaches and the Parmesan. Toss to combine, then add salt and pepper to taste and more olive oil, if needed.
NotesCook Notes: The pasta can be made ahead. Refrigerate after tossing with herbs, lemon zest and pepper flakes. Before serving, stir in the arugula, pickled peaches and Parmesan.