WD80EFRZ is supposed to be 8TB Red, how is it different from WD80EZZX ?
That hard drive model is not officially sold as a retail unit. As such, there are no official documents available to be used in order to compare both units.
Western Digital WD80EFRZ
WD - My Book 8TB External USB 3.0 Hard Drive - Black
Western Digital WD80EZZX
Western Digital Retail products
WD Red Pro WD8001FFWX 8TB 7200 RPM 128MB Cache SATA 6.0Gb/s 3.5"
WD Red WD80EFZX 8TB NAS Hard Disk Drive - 5400 RPM Class SATA 6Gb/s 128MB Cache 3.5"
Hope That Helps.