NEW DELHI, Oct 12 (Reuters) - India’s Zee said on Tuesday a push by U.S. investor Invesco for a management shakeup at the Indian media firm before its planned merger with Japan’s Sony Group was not related to any legal governance or business performance issues. Invesco, which has an almost 18% stake in Zee, has said terms of the planned Zee-Sony merger gave Zee’s founding family an option to ramp up their stake to 20% from 4% via methods the U.S. firm called “wholly opaque”, saying some shareholders would be unfairly rewarded at the expense of others. Reporting by Sankalp Phartiyal; Editing by Edmund Blair Our Standards: The Thomson Reuters Trust Principles.