Who is "El Mayo" Zambada, the Sinaloa drug cartel leader now in U.S. custody?

Ismael "El Mayo" Zambada, the top leader and co-founder of Mexico's Sinaloa cartel, eluded the reach of U.S. law enforcement for decades as the criminal organization evolved into the world's biggest manufacturer and smuggler of illicit fentanyl pills and other drugs to the United States.