Zeref Dragneel is 400+ years old, very few people know him and fewer than that who know his face or has seen him.
In Chapter 208: Death Preying, neither Elfman nor Evergreen recognize Zeref. Even Natsu doesn't remember him. Marijane seems to know a little about Zeref.
But we know that Zeref said that he wasn't dormant at all himself.
I don't know where did you find this information but, for some years he was inactive or in sleeping state. He awaken in Tenrou Island arc when he realizes Acnologia is coming.
As for Alvarez, He is known as Emperor Spriggan.
Zeref created this empire for the sole purpose of defeating Acnologia, obtaining Fairy Heart, and annihilating Ishgar.4 His plans regarding with Fairy Heart once captured was to relive his life with the Time Magic, Neo Eclipse. A plan the Spriggan 12 were not aware of.
When Makarov visit Alvarez to visit the Emperor Spriggan, he get shocked seeing Zeref as Emperor. Which also shows that how little the information of Zeref is available in present world. Makarov is one of the Ten Wizard Saints.
The image is from chapter 444: Emperor Spriggan, shocking face of Makarov when he sees Zeref as Emperor.