This goo is the same from the sludg hose that Jorge uses in their 3rd fight.
Swamp Zeds spit toxic goo from a distance that poisons whoever it hits. Other zeds like the swamp zed can also transform hostiles into zeds. For example if a zed infects an A.A.H.W agent the zed will have a agency suit and shades. They also can transform any hostile in to a zed and have the appearance of the person before it was infected. Zeds will sometimes hold weapons like guns or melee weapons, however they do not use them, and will still use unarmed attacks. Zeds will charge towards their targets and leap aggressively, grappling their target if they can't get out of the way. Zeds possess aggressive behavior similar to Asylum Patients and appear with green skin and visible mouths. Normal Zeds are the most common Zed type. They do not act hostile to other enemies in the stages. Zeds appear in Pit Stop starting from Wave 2, in The Haunting of Nevada House endless waves, and in The Murder Room with Honk Zeds. Zeds also constantly attack survivors and Bandits if they get into their line of sight. Zeds are incredibly drawn to alarms, and if Sanford and Deimos activate them, swarms of zeds will spawn.
Throughout the Residential Sector, zeds are a reoccurring and plentiful enemy that you see constantly. You encounter them in the second room as Sanford and Deimos. Zeds first appear in the Residential Sector in Beat the Streets.