Not much is known about Colonel America's past prior to his zombification, though it is believed to be similar to that of Captain America from Earth-616. He was once a sickly young man who attempted to enlist in the United States Army during World War II, only to be turned away due to his various health issues. However, he later signed up for an experimental procedure in which he was injected with a potent "super-soldier serum", greatly enhancing his strength, agility and reflexes and eliminating all of his previous ailments. Rogers would contribute significantly to the Allies' victory in the war, and decades later he served a brief term as President of the United States, later resigning from office for unknown reasons.
As a zombie
The Hunger Gospel arrived on Earth in the form of an undead Sentry, who appeared in the middle of New York following a strange purple lightning storm. The Avengers, led by Colonel America, went to investigate and found the extra-dimensional former superhero devouring the flesh of innocent citizens. Driven by the zombie virus' attraction to meta-humans, the Sentry attacked the Avengers, with Colonel America being the first to be bitten and infected.
His mind twisted by the infection, Rogers succumbed to the hunger and led the Avengers in attacking and devouring all living humans in sight as well as infecting other superheroes. The Colonel's first victim was fellow Avenger Spider-Man. Though briefly sated after eating several victims, Rogers could not maintain a lucid state of mind and quickly fell back into hunger. He and the other super-zombies quickly gave up trying to find a way of stopping the infection and decided to continue hunting the living, battling against any surviving heroes and villains that tried to stop them.
Within three days, the meta-human population, heroes and villains alike, have devoured virtually all humans on the planet. Some time later, Reed Richards creates a dimensional transporter device which the zombies can use to invade other realities for new meat. However, his device is destroyed by former mutant terrorist Magneto, one of the only non-zombies left on Earth. The zombies are outraged and attack Magneto, with Colonel America leading the charge. However, Magneto uses his magnetic powers to manipulate Rogers' shield, forcing the Colonel to scalp himself. This does not kill him, however, or even remotely debilitate him, and he continues to pursue Magneto along with the other zombies. They eventually catch up to the Master of Magnetism and rather than infect him, they completely devour him.
Some time later, the cosmic explorer known as the Silver Surfer visits Earth, warning that Galactus is on his way. The zombies aren't interested in what the visitor has to say and they attack and devour him. This, in turn, grants those zombies who fed on the Surfer a portion of the Power Cosmic, including Colonel America. A short time later, Galactus arrives and is enraged by what the zombies have done to his herald. Colonel America and the empowered zombies attack Galactus, but he is far too powerful for them. However, Galactus' presence attracts an army of zombified heroes and villains to New York and they all battle the Devourer of Worlds together, keeping him distracted whilst the Power Cosmic zombies try to jerry-rig a device that can channel and amplify the Power Cosmic they have gained from the Silver Surfer. The device works and fires an immense beam of cosmic energy that disables Galactus, leaving him vulnerable.
The undead villains who kept Galactus at bay argue that they should be allowed to eat Galactus as they did all the work, but Colonel America and the other empowered zombie heroes disagree and a battle breaks out. During the battle, Rogers is confronted by his long-time arch-enemy, the Red Skull. While Red Skull had never been a physical match for Rogers before, Rogers never had an obvious weak spot before: the exposed brain matter sitting in the Colonel's gaping head. The Skull plunges a hand into Rogers' open cranium and scoops out the rotten brain matter, killing his nemesis once and for all. Or so it appears...
Not Quite Dead...
Forty years after his supposed "death", Colonel America's brains are salvaged by Forge and transplanted into the body of T'Channa, son of T'Challa, the Black Panther. While the transplant was a success, the brain was so badly damaged that the result was a crazed Colonel America that seemed to be stuck in the past, reliving his previous military days and unable to focus on anything aside from battle.
Prior to the zombie infection, Colonel America was a specimen of peak human efficiency. He possessed strength, speed, agility, endurance and reflexes well above the human norm, thanks to the Super-Soldier serum administered to him when he first joined the US military. He was equipped with a unique circular shield made from vibranium which he wielded to shield himself from attacks and also to attack by throwing it like a discus or boomerang.
After becoming a zombie, Colonel America seemed to retain all of his abilities. Whether his physical abilities were in any way hampered by the necrosis brought on by the infection is unclear.