Varicella-Zoster and Epstein-Barr are both viruses.
Varicella-Zoster virus causes two main diseases:
Varicella- a.k.a chicken pox in children, is generally benign and only becomes
serious in immune-suppressed cases.
Zoster is the disease caused by reactivation of the latent varicella virus. I
believe it is commonly referred to as Shingles
Epstein-Barr virus causes mono (mononucleosis) in adolescents and young adults.
As with most organisms, you can also end up with some strange and rare complications
but these are the major and most common diseases.
Hope it helps