SEOUL :South Korea's financial market watchdog is investigating whether Korea Zinc's decision to issue new shares involves any unfair practices, it said on Thursday. The world's top zinc refiner on Wednesday announced a plan to issue shares worth about $1.8 billion in a move perceived by analysts as strategy to fend off a takeover by Young Poong and MBK Partners, sending its stocks plunging. Two days earlier Korea Zinc bought back shares at a higher price and pledged to cancel all of them to