Endurance in boxing is more than just about aerobic capacity or the ability of the muscles to repeatedly go anaerobic in short, explosive bursts and then recover. It is about being able to make huge demands of your body and have it respond with ease. It's about being able to explode into action and then bounce around with ease. It is about being strong and fast and having great core and superb balance and fast recovery time. You're doing High Knees after each exercise here (and you'd better make sure they are high by bringing the knee to your waist height each and every time) using the same muscles you would as if you were preparing for the biggest fight of your life. No rest between sets for that all important EC.
Extra Credit: NO REST BETWEEN SETS.