OP, what are you looking for in a player?
Which zen do you have now? a nano? a vision? Are you looking for a smaller flash player or a larger harddrive one?
If it's flash, the Sansa is a great flash player, with a richer featureset than and at a lower cost than the ipod. The expandable microsd slot is also a fantastic feature. Allowing you to constantly rotate out 1-2gbs of music- very good for when the music feels stale on the smaller players.
For harddrive based- the cowon's iaudio x5 is a solid all-around player. The video playback is not as great as the ipod, but everything else is on par or better. Again, far greater featureset out of the box. Also compatible with rockbox.