A long-awaited city audit of the Denver Zoo landed Thursday without major demerits but renewed questions about the use of recycled water in animal exhibits. The audit was the first undertaken by the city since the Denver Zoological Foundation took the reins of the City Park installation six decades ago. And it came after months of resistance by zoo officials to the city auditor’s office — until Auditor Tim O’Brien publicly fired off a letter to Mayor Michael Hancock in April. O’Brien said Thursday that Denver Zoo officials eventually cooperated fully with the audit, which was allowed explicitly by the zoo’s most recent 25-year cooperative agreement with Denver Parks and Recreation. Zoo president and CEO Shannon Block and Denver Parks and Recreation executive director Allegra “Happy” Haynes agreed to implement all eight recommendations in the audit.