How to Connect a Macbook Pro A1501 to an HP Z24i Monitor?
I have this same setup, but with an older Macbook Pro (A1278). 

Simply get a mini DisplayPort to DisplayPort adapter, and use DisplayPort only. The Thunderbolt port on your Macbook Pro is ALSO a mini-display port and it is compatible with a mini-DisplayPort connector.

Here is an example from monoprice.com http://www.monoprice.com/product?p_id=6006