Zelter’s firm, Apollo Global Management, is slowly picking off pieces of the finance arm that nearly brought down General Electric Co. Apollo has already bought billions of investments once managed by GE Capital, and it’s been sizing up GE’s insurance and jet-leasing businesses, people familiar with the matter have said. GE’s new leader, Larry Culp, is working to turn around the embattled conglomerate, which expects negative cash flow this year in its industrial businesses. It’s quite a switch for both GE and Apollo, the buyout giant led by Leon Black.