Preparation Bring 3 quarts water to a boil in a 5- to 6-quart pot, then cook black-eyed peas, partially covered, until tender, about 20 minutes. While peas are cooking, cut zucchini and fennel into 1/4-inch dice. Whisk together scallions, dill, vinegar, lemon juice, mustard, pepper, cayenne, and 1 1/2 teaspoons salt in a large bowl. Add oil in a slow stream, whisking until emulsified. Add zucchini and fennel to dressing. When peas are tender, transfer with a slotted spoon to a sieve set over a large bowl, reserving cooking water in pot, and cool peas slightly, then add to salad. Return water to a boil and add remaining 1 1/2 tablespoons salt, then cook corn and edamame, uncovered, until tender, 6 to 7 minutes. Transfer to sieve to cool slightly, then add to salad and stir to combine. Cool salad completely and serve chilled or at room temperature.
Preparation Bring 3 quarts water to a boil in a 5- to 6-quart pot, then cook black-eyed peas, partially covered, until tender, about 20 minutes. While peas are cooking, cut zucchini and fennel into 1/4-inch dice. Whisk together scallions, dill, vinegar, lemon juice, mustard, pepper, cayenne, and 1 1/2 teaspoons salt in a large bowl. Add oil in a slow stream, whisking until emulsified. Add zucchini and fennel to dressing. When peas are tender, transfer with a slotted spoon to a sieve set over a large bowl, reserving cooking water in pot, and cool peas slightly, then add to salad. Return water to a boil and add remaining 1 1/2 tablespoons salt, then cook corn and edamame, uncovered, until tender, 6 to 7 minutes. Transfer to sieve to cool slightly, then add to salad and stir to combine. Cool salad completely and serve chilled or at room temperature.