In 2374, Zek approached the Terran Rebellion's leader Miles "Smiley" O'Brien on Terok Nor with the offer of a Romulan cloaking device for the Defiant. O'Brien had harshly dismissed the "doddering old Ferengi" as "a worthless whining prune." However, Zek was able to deliver on his promise and secured the cloaking device for the rebellion. This gave the rebels a major tactical advantage over the Klingon-Cardassian Alliance after it was installed aboard the Defiant. Furthermore, O'Brien and the other top engineers in the rebellion were able to reverse engineer its internal workings and construct others.
By 2375, Zek had been made a general. His procurement of the cloaking device earned him an ally in the form of General Julian Bashir and the two began to sway opinions within the rebellion against O'Brien and his methods. While their never voiced their true intentions, Smiley was certain that they intended to either have him removed from his leadership position or substantially reduce his influence so that they could run the war against the Alliance. Going behind O'Brien's back, Zek, Bashir and their supporters captured the abandoned Alliance ore processing Nor-class space station Empok Nor in the Trivas system with the intention of converting it into a rebel shipyard. To that end, they conducted raids on numerous Alliance targets to gather the necessary equipment and material as well as large quantities of kelbonite, a refractory metal which was capable of interfering with sensors. Over the course of several months, they were able to construct twelve Defiant-class warships at Empok Nor, all of which were equipped with reverse engineered cloaking devices. This was accomplished by running the station's primary fusion reactors at 105% around the clock. The first vessel off the assembly line was the Capital Gain under the command of Zek.
In spite of the presence of the kelbonite, O'Brien was concerned that the Alliance would eventually realise that the rebels were staging a major shipbuilding operation at Empok Nor as, taken together, the raids pointed in that direction, particularly since they all occurred within a five lightyear radius of the Trivas system. Although Zek and Bashir dismissed his concerns as baseless, they were in fact well justified as Kira Nerys, the disgraced Intendant of Bajor, determined the true reason behind the raids and took the information to Captain Kurn, the commanding officer of the IKS Ya'Vang, in the hope of restoring her position in the Alliance. Kira and Kurn immediately began planning an attack on Empok Nor.
As a test of the Capital Gain's capabilities, Zek suggested that his ship and the Defiant launch an attack on the Cardassian sensor station Vareth Dar, which possessed the most advanced signals-intelligence hardware at the Alliance's disposal. Following the destruction of Vareth Dar, Zek requested that O'Brien join him in destroying an unarmed Cardassian farming colony on the fourth planet in the system. However, O'Brien refused to eradicate the planet's civilian population as he believed that doing so would make him no better than the Alliance. Furthermore, he threatened to destroy the Capital Gain if it opened fire on the planet.
Following their return to Terok Nor, Zek and Bashir accused O'Brien of having lost his nerve as he had recently fallen in love with Keiko Ishikawa. When Zek accused Keiko of being an Alliance collaborator, O'Brien had to be restrained from attacking the Ferengi by his fellow rebel leaders Cal Hudson and Michael Eddington. He and Bashir then proposed dealing a crippling blow to the Alliance by launching attacks on both Cardassia and Qo'noS. Although General Kasidy Yates was reluctant to attack civilian targets, she nevertheless agreed to participate in their plan, as did Hudson. However, Eddington sided with O'Brien.
While Zek and Bashir were amassing their fleet at Empok Nor, the Ya'Vang launched its attack on the station. Within minutes, they were able to destroy Empok Nor by targeting its primary fusion reactors as well as all of the Defiant-class ships other than the Capital Gain. After the vessel was boarded by Kurn and the Intendant, the latter informed Zek that his primary universe counterpart, whom she had met earlier that year, was the Grand Nagus of Ferenginar. She taunted him by telling him that the Zek of the primary universe was the chief executive of an economic empire and the richest Ferengi in the galaxy while the only thing that he was in charge of was a "band of criminals." After Zek told her to shut up and called her a "whore," she stabbed him in the carotid artery, killing him instantly. (DS9 - Mirror Universe novel: Saturn's Children)
After the victory of the Terran Rebellion in 2378, O'Brien mourned Zek's death in spite of that he and Bashir "had acted more like his rivals than his allies." (ST - Mirror Universe novel: Rise Like Lions)