Rough chop the watercress - the object is to leave the greens in large pieces - do not over chop. If the leaves are small, simply pick them from the stems. Place in a large mixing bowl. Rough chop all the herbs and place them with the watercress. Add in the grated lemon rind.
Drizzle with a little of the lemon vinaigrette, then toss lightly to coat the greens.
Serve.
For the Vinaigrette:
Whisk the lemon juice, Dijon mustard, Kosher salt, and pepper together, and then stream in the oil while constantly whisking to emulsify the dressing.