Zia spends much of her time plugged into the Ultranet, and in doing so somewhat disappoints and annoys her mother. When she is not plugged in, she is shown to be sarcastic and somewhat arrogant around her mother. Her rebellious nature leads Lisa to think that Zia doesn't respect her, stating that Zia thinks she's a "ruthless tyrant", and questioning how she had a daughter that ended up like her brother.
Lisa became pregnant with Zia in 2027, as seen in the montage of family photos, and the next year, in 2028, Lisa and Milhouse are seen with an infant Zia. So Zia was born in either late 2027 or 2028, making her either 13 or 14 years old. She is then shown in Lisa's family Christmas photo for 2041 with her parents on their couch. Zia looks bored and Zia looks a lot like her mother, due to apparently having most of Lisa's genes. Zia's hair is similar to Lisa's, except it is rounded instead of pointed, and she has a lock of blue hair, which may have come from Milhouse's genes. Her face also looks like Lisa's, except she usually looks uninterested or angry. She has a changing tattoo on her left arm, one of which is the Taoist symbol the Yin Yang. She wears a purple crop top, a pink skirt with a grey belt and purple straps on the side, pink and purple boots, and a pink bracelet on her left arm.
According to Milhouse, the genetic engineering technology allows Zia to have all the good features, thus containing none of his genes. This seems like a joke, given that she is quite different from Lisa, and the definition of the parent-child relationship make the two share 1/2 the same genes.
Worried, Lisa enters the Ultranet to check up on Zia despite her own feelings and Marge's advice. Lisa finds Zia's Ultranet room to be filled with things dealing with science and other studies, and there are posters in her wallof women such as Joan of Arc, Marie Curie, and Lisa herself. Zia appears and then questions what Lisa is doing there, Lisa tells Zia that she's sorry for invading her privacy, and that she only did it out of concern, but she's glad because she learned that her daughter looks up to her. Zia replies that she looks up to both of her parents, but she especially looks up to her mother, and they both hug. As they do this, a door to another room, a dance club, opens slightly behind them. Zia closes the door before her mom notices.
- Zia's last name is highly disputable. It is heavily implied that Lisa takes Milhouse's surname. However, Zia's Ultranet Room reads on the front "Zia Simpson". One reason could be because Zia has a better relationship with her mother (Lisa Simpson) than her father (Milhouse Van Houten).
- Zia has a tattoo on her upper left arm that is evidently a hologram or some other similar device, since it changes into several different designs. These designs include:
- Zia has a better relationship with her mother than her father.
- Zia plays a music with her Electronic Synthesizer with Jenda because Zia and Jenda mastered of playing music.