I wouldn't call most Zetas, or most cartel members in general courageous. Even if we're leaving morality aside.

The media likes to hype them up as highly-trained, professional, James Bond-like killing machines, but the truth is that they are nothing new. Their kind have existed throughout Africa for decades. Kids born in poverty, brainwashed, armed, taught the basics of not shooting themselves with their own guns(if that) and used as cannon fodder to kill each other. All of them are blasted out of their minds on coke, heroin and booze 99% of the time.

Are they dangerous? Yes. Brutal? Sure. Courageous? Fuck no. Though? No.

Coincidentally, I've been reading the book "El Sicario: Confessions of a Mexican Cartel Assassin". Apparently the protagonist was one of the best sicarios in Mexico, responsible for hundreds of killings. Even he confesses he was coked up to the eyeballs most of the time and he doesn't even remember part of the shit he did. He also said that, even though the level of violence in Mexico increased, the shooters on the street today are far worse quality-wise than those of even 5-10 years ago. They're not "real sicarios", just unskilled, incompetent morons.