What this means is that the Combined Gender Identity and Transsexuality Inventory has classified your internal gender identity to be essentially androgynous, both male and female at the same time, or possibly neither.
-- Z reading the COGIATI (chapter 1)

Importance: This quote establishes why Z prefers to go by they and them pronouns, even though many other people in her life refer to them as she or her. Z really does not feel that they belong to a specific gender, nor do they feel like a female. This is something that clearly affects how they see the world and themselves. More importantly, it is made clear that the results of this test are something that Z only recently received. This means that they are still coming to terms with them, even though it is clear that they have felt this way for quite some time.

Zombies are different: most have no magical power of their own, since...
-- Everything You Need to Know About Monsters (chapter 3 paragraph 84)