Premium Domains work a little differently than normal domain purchases do. If you search for a domain at Zname.com and it says the domain is "Premium," it means that someone owns it and is willing to sell the domain name for the price listed. Zname.com is not able to negotiate the price for you.
If you wish to purchase a Premium Domain, the process for doing so is slightly different than that of a normal domain name. With a Premium Domain name, a special level of review is required for the order, so the domain name will not go into your account right away. But don't panic—you should see it listed in your account once the review process is completed. While it is being reviewed, the domain will still show as available for purchase. Keep in mind that if anyone tries to check out and buy it, the order would fail, and they would not be able to take it from you during the review period.