Tesla Inc.’s latest C-suite shake-up will thrust a 34-year-old relative unknown into the spotlight as financial chief of one of Silicon Valley’s most heavily scrutinized companies.

The announcement late Wednesday showed Elon Musk’s penchant for surprising investors, when at the end of a quarterly analysts’ call the car-making CEO unexpectedly said he was replacing his longtime confidant, Deepak Ahuja, with “Zach,” without providing his last name.

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