In a medium bowl, combine the vinegar, cranberry juice, honey and salt and white pepper to taste.
Slowly add the oil and whisk until the oil is incorporated into the vinaigrette.
Chop the cranberries and add them to the vinaigrette.
Stir to combine. Set aside.
Cut each zucchini and yellow squash in half lengthwise. Drag the tip of a spoon lengthwise along the cut half to remove the seedy core.
Slice each half into 1/4-inch-thick half-moon slices. Steam the squash until the slices are just cooked through. The white flesh will start to look opaque and the slices will start to wilt. Be careful not to overcook. Transfer squash to a large bowl.
Add the dressing gradually to the squash--just enough to keep the salad moist--and toss to combine. (You probably will not need all the.
dressing.) Set aside for 5 minutes. Transfer to a serving dish. Serve immediately.
Do Ahead Tip:
The squash can be sliced, covered with plastic wrap and refrigerated ahead of time. The dressing also can be made hours in advance, then whisked together again before adding to the squash.