Nzi was born to a semi-wealthy trading family in Zuldazar. As he was not the gender his parents hoped for, he was put forward to be raised by the tribe (or, rather, the neighborhood). They were rather hoping for a daughter with which they could marry off to one of the many, much more wealthy princes. Sure, their son could marry someone else's daughter and get a very fine dowry, but it just wouldn't be the same.
As a child, he essentially had his run of the place with a whole mob of other whelps. The only real bad part of his childhood is the fact that he never managed to impress his parents. He was better off than most his age, though, seeing as he made it through his early years without near death experiences or other major traumas.
The very first chance they got, Nzi's parents sent him off to apprentice for a scribe. By that point, they had the daughter they'd wanted and they no longer had any use at all for their son. From that point on, he only ever knew his family through messages and occasional visits home (the former because it was proper, the latter only because his sister insisted). That was largely okay with him.
Rather than learn many meaningful things from his crotchety old master, Nzi preferred to spend as much time not being present for either lessons or work. It was his habit to go haring off into the city or the wilderness, drawn to trouble. He enjoyed climbing to the highest heights he could find. When he learned about kites, that became his new obsession, and his way of paying homage to the many Loas and spirits his people revered. Needless to say, he didn't get much writing done.
It is Zul's rise to power that marks a turning point in Nzi's life. While he appreciates the idea of all trolls united under one king for real, he is not so fond of the methods being taken to do it. It looks as if Zul wants Hakkar to rise again, and to bring both the Alliance and Horde down on the Zandalar's heads. With very little to keep him in Zuldazar, Nzi chose to flee, offering his services (such as they are) up to the Darkspear. He is not the only Zandalari to choose to defect, nor is he likely to be the last.
Settling into the new tribe has not been entirely easy. After all, he could be a spy, or worse. But, he's pretty satisfied with his lot.