It's a Z fare... or it really should be. For whatever reason, United publishes its domestic non-differential premium fares using Economy basis letters. For the fare YAZ14UPN, which is a regular published fare, the Z in third position is the booking code, and the UP in sixth/seventh position indicates it's essentially a premium fare. Because it has a Y in first position, the fare header sometimes says "Economy Restricted" or similar and may be categorized as such by your booking engine. But it is, and ought to be treated as, a Z fare for all useful purposes.

The corporate part of the fare is just the /8N35, which references the corporate discount to the base fare (which is probably 35%).

For more context: A Comprehensive Look at Domestic First Class Monetization (FCM) on United