Says everything is experiencing confusion and nausea, but no pain. he had also discovered that he is having problems with his lungs, kidneys, and liver. what illegal drug is zayden most likely abusing?

Zayden is most likely abusing Depressants 
Liver are failing is because of depressants. When taking depressants and overdosing like cough syrup can cause the organs go into a state of depressant. Which causes the organs to have problems and can kill him.

Zayden is most likely abusing alcoholic beverages. Alcohol causes harm to your liver and kidneys which could lead him to having to get a new one donated.