Line medium-size bowl with double thickness of cheesecloth. To extract some moisture from zucchini, coarsely grate unpeeled zucchini into prepared bowl. Sprinkle with vinegar, sugar, and 1/2 tsp salt. Toss gently; cover; set aside 1 hour. In food processor, with chopping blade, process parsley and chives until very finely chopped. Gather ends of cheesecloth; squeeze zucchini to drain out as much liquid as possible. Add drained zucchini to processor; process until smooth. Add softened cream cheese, remaining 1/2 tsp salt, and the pepper. Process until well-combined. Press zucchini pate into small bowl. Cover and refrigerate several hours or overnight.