This model motherboard over to DDR3-1600MHz is oc mode,so if you want to setting DDR3-2133MHz must be depends the hardware constitution (maybe motherboard or memory or CPU)
You can try to set the memory to DDR3-2133MHz,but we suggest you can check this model memory work voltage first then into the bios avvanced to setting...
Please help to upgrade the motherboard latest version bios before to setting the memory frequency
The latest version file download link: 1604
http://www.asus.com/ROG/MAXIMUS_V_FORMULA/#support_Download_29_MAXIMUS-V-FORMULA-ASUS-1604