HP has also said it wants to put Windows 7 on enterprise tablets.

Zeen's surprise entry adds another layer of mystery to HP's plans of selling tablets with multiple operating systems, analysts said. It might take some effort to explain differences between the devices to customers.

"You have to be able to explain to customers the subtle or specific benefits of the products. That's a process and exercise that HP is used to as it supports Windows and Linux on the desktops and multiple operating systems in the server world," King said.