The title is stylized in the episode as Marching out the ZOMBIES.
Mayuri says the zombified Toshiro, Kensei, Rose and Rangiku have dark red skin. However, it's actually light brown. Unless this is a trick of the light; red blood turns this color when it dries.
Yumichika and Charlotte both realize Gigi is a cisgender male. However, Tite Kubo confirmed Gigi is a trans woman. Which explains why Gigi becomes so wrathful; they are denying her gender identity.