From the opening paragraph of the Wikipedia article on Los Zetas:[1]
The origins of Los Zetas date back to the late 1990s, when commandos of the Mexican Army deserted their ranks and began working as the enforcement arm of the Gulf Cartel. In February 2010, Los Zetas broke away and formed their own criminal organization, rivalling the Gulf Cartel.
Needless to say, going after some gang is likely to be different than going after a gang of ex-commando military personnel, and that's before you factor in that there's probably a steady stream of military that still leave to join Los Zetas and that they probably still have active military contacts...
Not only are the Zetas not full of military any more, they are fighting constantly between old school and CDN (when they aren't fighting golfos). The current organization is a shell of what it was.
It was a red queen's race that they lost by attracting too much attention. The original cadre of special warfare operators has been eliminated, and their escalation in violence and sophistication of direct action was emulated by others. Cooperation with the government and subverting the state is more powerful than killing entire towns.
The origins of Los Zetas date back to the late 1990s, when commandos of the Mexican Army deserted their ranks and began working as the enforcement arm of the Gulf Cartel. In February 2010, Los Zetas broke away and formed their own criminal organization, rivalling the Gulf Cartel.
Needless to say, going after some gang is likely to be different than going after a gang of ex-commando military personnel, and that's before you factor in that there's probably a steady stream of military that still leave to join Los Zetas and that they probably still have active military contacts...
1: https://en.wikipedia.org/wiki/Los_Zetas