Here's a breakdown:
* "Zmęczony" is used for a male subject.
* "Zmęczona" is used for a female subject.
* "Zmęczenie" is used for a general state of tiredness or fatigue.
Here are some examples:
* Jestem zmęczony. (I am tired.) - Masculine
* Ona jest zmęczona. (She is tired.) - Feminine
* Czuję zmęczenie. (I feel tired.) - Neuter