About 35 minutes before serving,shred enough to measure 1 cup. Set remaining zucchini aside.Shred Monterey Jack cheese.In a medium bowl,grate onion.Add ground beef,bread crumbs,ketchup,and 1/2 tsp. salt.Mix well.On waxed paper,par ground beef mixture into a 11 x 8" rectangle. Sprinkle shredded zucchini and cheese over beef mixture. Starting on a long side,roll meat mixture around filling,jelly roll fashion,lifting wax paper to help shape roll.Press seam and sides to seal. Carefully,transfer beef roll,seam side down,to a 2 quart oblong baking dish.Microwave cook,covered with waxed paper on high 5 minutes.Then on medium (50%) 15 minutes.Let stand covered. Meanwhile,in a 10" round baking dish,melt butter on high 30 seconds.Add zucchini.Cook,covered with plastic wrap,on high 3 to 4 minutes,until just tender.Sprinkle with 3/4 tsp. salt after cooking. To serve,cut beef roll into 12 slices on serving platter.Spoon zucchini along side of meat,Makes 6 servings.