I can tell you very little about Zangaki, since so little appears to be known about them. Them? Yes them, because there were apparently two brothers of Greek origin who were famous photographers in roughly the period of the 1860s through 1880s. Their initials were G. and C., and their work was simply signed Zangaki. They specialised in images of Egypt and Palestine and worked, I read, out of Port Said. Apart from those few facts, I can find little else about them.