definitely.

For the OP: PZ is a special inventory bucket used for upgrades. It's rare to find it, but when you do, you can purchase an economy ticket and then clear an upgrade immediately. All MileagePlus members are eligible to use it with a Miles+Copay award, but it does have its downsides -- if there are problems on the day of travel, and you have to get re-routed on another airline, you're likely going to be in economy. With a business class ticket, there's a better chance you can still end up in business class.