She and Varrick were placed in Republic City's jailhouse when it was discovered that the latter had hired a waterbending gang to abduct President Raiko. However, when a merged Vaatu and Unalaq began attacking Republic City, the wall to their cell was obliterated by one of Vaatu's vines, which Zhu Li and Varrick used as an opportunity to escape. She then took refuge in Zaofu with Varrick in book 3.
Three years later, she joins Kuvira's army with Varrick, and assists him with collecting and experimenting with spirit vines. After the energy from the vines destroys the machinery and almost blows her off the moving train, Varrick saves her, although only to have someone to clean up the resulting mess. After Bolin helped she and Varrick escape via mecha tanks, Zhu Li helped them fend off Baatar Jr. and two other soldiers, only to be captured and sentenced to a correctional facility. At this point, she turns on Varrick because of his lack of gratitude and openly pledges herself to Kuvira's cause. She is later appointed as Baatar Jr.'s assistant in construction a new superweapon after the spirit vine research is destroyed.
When the testing for the new superweapon began, Kuvira intended to test it on an abandoned town, and Zhu Li began sabotaging the machinery without Kuvira's knowledge. However, as Baatar Jr. continually noticed that parts of the machine were either damaged or missing, Kuvira began suspecting Zhu Li. When she was discovered, she told the warlord that she regretted nothing, and that she was a monster. Kuvira ordered her guards to chain her in the abandoned town so she would be destroyed along with it. She was rescued when the Beifongs interfered, and after escaping, she informed them that Kuvira planned to attack Republic City in two weeks' time.
Upon returning to Republic City, she warned the president about Kuvira's attack plan and reunited with Varrick. She apologized for what she said during her apparent betrayal and confessed possible romantic feelings for him, and Varrick forgave her, only to tell her to get to work on the assembly line, while remaining oblivious to her confession. This caused Zhu Li to grow angry and demand that she be treated as an equal instead of an assistant.
Zhu Li assists Varrick in the battle against the Earth Empire in Republic City, helping him use an electromagnetic pulse to stall the giant mecha suit carrying the spirit energy cannon (though it ultimately fails). Varrick proposes to her before they depart for their final plan against Kuvira, which Zhu Li gleefully accepts. After Kuvira surrenders and the Earth Empire is dissolved, Varrick and Zhu Li are married on Air Temple Island.
- Her role is similar to that of Mercy Graves. Zhu Li works for Varrick much like how Mercy serves Lex Luthor, and both those they serve are ruthless businessmen. Despite the less than legal, morally questionable actions committed by their bosses, they don't seem to complain about it at the end. For example, Mercy still served Lex Luthor even though he showed no care for her when Braniac endangered her life, and Zhu Li served Varrick in prison even though his schemes were exposed. In addition, Zhu Li has had feelings for Varrick, similar to how Mercy had feelings towards Lex Luthor.