Hindustan Zinc reported a more than two-fold rise in quarterly profit on Monday, helped by higher zinc and silver prices and increased production. Consolidated net profit was at Rs 6,412 crore for the three months ended September 30 as against Rs 2,649 crore a year earlier. Net profit margin climbed to 42% from 31% a year ago. The Vedanta group company has operations spanning the mining, processing and refining of zinc, lead and silver, as well as wind power generation