Two-time founder Rujul Zaparde knows a thing or two about resilience and learning from failure. After dropping out of college to build FlightCar, he worked as a PM at Airbnb, and later as a visiting partner at YC. In 2020, he co-founded Zip, a procurement software company that has since raised $370 million and reached a $2.2 billion valuation. In this conversation with YC's Dalton Caldwell, Rujul demystifies the world of enterprise sales, shares his hard-earned lessons about scaling a business from zero, and explains how founders can use first-principles thinking to better approach the challenges of building a startup.