Z40 was one of the first to join the Gulf Cartel’s security arm, the Zetas. When Zetas commander Arturo Guzman Decena was killed in 2002, he rose through the ranks. In 2006, he was stationed as the "plaza" boss in Nuevo Laredo, the Zetas’ longtime base of operations. Near 2007, he was sent to Veracruz following the death of a high-ranking member of the group. He took control of that drug trafficking corridor, while simultaneously taking over other illicit industries such as trade in pirated DVDs and CDs, and human trafficking. He’s also thought to run the Zetas' operations in Guatemala, where the group has established bases in the northern states of Peten and Alta Verapaz.
Several of his family members also became involved in crime. His brother and uncle laundered money on the Zetas' behalf in the US, using a horse-breeding company as a cover-up. They were captured after a raid on US territory in 2012.
In July 2012, the Zetas reportedly split into two factions, one side headed by Z40, the other by Heriberto Lazcano, alias "Z3." The rival capos each accused the other of betrayal and became embroiled in a bitter and violent power struggle. In October 2012, Mexican security forces reported shooting and killing Z3, leaving Treviño as the most senior Zetas commander. In October 2012, a Zetas splinter group comprised of opponents of Z40 announced they had formed a new group, Los Legionarios (the Legionaries), with the express purpose of waging war against Z40 and his organization.
Treviño worked to consolidate his hold over his Zetas. However, he was captured in July 2013 in Anahuac, a town southwest of Nuevo Laredo.