Greene said in a corporate blog post that she originally planned for a two-year stint when she joined Google in 2015 to run its enterprise business, but ended up working an extra year. She said that she would remain on the board of Google’s parent company, Alphabet.

“Now, after an unbelievably stimulating and productive three years, it’s time to turn to the passions I’ve long had around mentoring and education,” Greene wrote. “The mentoring will include investing in and helping female founder CEOs who have engineering or science backgrounds.”

Greene is a high-profile Silicon Valley technology executive who co-founded enterprise company VMware, which helped popularize the virtualization technology used by companies to improve the efficiency of their data center servers. Analysts viewed Google’s hiring of Greene as a way for it to grow its cloud computing business, which competes against bigger rivals like Amazon Web Services and Microsoft.

Under Greene, Google consolidated its cloud computing products under one unit and rebranded its workplace software products as G Suite. It also made numerous acquisitions like the data science community startup Kaggle and enterprise software company Apigee, while also debuting several machine-learning services for businesses and embarking on a massive hiring spree. Alphabet CFO Ruth Porat has said several times during the company’s earnings calls that most of Google’s hiring is in its cloud business.

But while Google has landed big customers like Target, Colgate, and the parent company of the popular Snapchat messaging service, technology analysts consider the search giant to be trailing Amazon and Microsoft in the enterprise space. That said, Google said in February that its cloud business crossed a milestone by collecting $1 billion in quarterly revenue for the first time, but it has not disclosed any of the unit’s sales figures since then.

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Meanwhile, Kurian left Oracle in September, reportedly due to disagreements with Oracle’s executive chairman Larry Ellison over product decisions related to Oracle’s cloud computing service. Kurian is also a long-time enterprise technology veteran whose twin brother George Kurian leads the data storage and management company NetApp.

“I have deep appreciation for everything Diane has done and I’m super happy that we’ll continue to benefit from her wisdom as she continues serving on our Board of Directors,” Google CEO Sundar Pichai said in a statement. “We’re really excited to welcome Thomas whose product vision, customer focus, and deep expertise will be a huge asset to our growing Cloud business.”