Zenith Administrators Inc., America's largest third party employee benefit program administrator, has signed a 10-year deal at 221 Main St., a 16-story, 350,000-square-foot office building located in San Francisco's South Financial District. Zenith subleased the entire 2nd floor, comprising of 23,056 square feet of Class-A office space. The suite was previously occupied by a failed dot com, The Car Club. The new tenant is relocating from 301 Mission St., a building scheduled to be demolished in the next 12-18 months to make way for a new development. Zenith's deal involves a 3-year sublease with a 7-year extension valued to be in the high $20's per square foot annually, full service. Markus Shayeb and Ben Durham with HC&M Commercial Properties in San Francisco represented the sublessor. Christian Lustic with CB Richard Ellis represented Zenith Administrators. The landlord, C&C Investments, represented itself in the direct deal.