Humans are not really native to the Zulu sector, or even this galaxy.
It is said that in a time in the past, Humans came to the Zulu sector through an accident involving hyperspacial travel from some large scale disaster in a different galaxy. The vessel which brought them to Zulu had to be abandoned and colonies were set up in the G2 sector of Zulu.
The colonies initially lost contact and hyperspace technology for a number of years, until one world discovered some of the ancient drives that brought them back to interstellar pathways. Upon discovering this, and a few other strokes of luck, conquering the nearby Human colonies was an easy thing and the Razu Empire was formed, with a Romanesque structure to it. The empire spread to a number of star systems until contact with the Cibosans and the Rasafac were made.
Captain Defanu Tanaka was a member of the Razu for a number of years to pay off a few debts to Razu society. He made the rank of Admiral before leaving the Razu military to join the war against another species, the Shyedarians, who were threatening every angle of existence.
Sadly, it was not the Shyedarians that brought down the Razu Empire, it was internal power struggles and the Razu empire fragmented into two structures, the Shirex and the Nostras. The Nostras remain very open with the Cibosans and the Rasafac, but the Shirex are very xenophobic and maintain absolutely well defended borders against anyone not Human.
The Nostras and the Cibosans maintain excellent relations with each other, concreted by Defanu Tsoami, who accidentally crashed landed on a world where Nostras were doing a very harsh military training excercise.
Humans can be found anywhere, colonies exist in almost all parts of the Zulu sector.