How did Jor-El stand a chance against Zod?

Just because Jor-El was a nerd doesn't mean he is a weakling. Jor-El is a skilled fighter and pilot in the comics.

It doesn't matter what skills they possess, because in that scene you can see that Zod was surprised to see Jor-El do something so drastic. Zod was naive, in my opinion, even until the climax. He actually thought Kal-El would somehow give up on the earthlings. He says during the climax fights that his entire race is all gone, quite emotionally.

My point is, when he sees that Jor-El is ready to go the distance, he is surprised and that's when Jor-El gets him - while Zod is off-balance. He wouldn't be able to do that in an open situation, granted.

And what about the other scene when Jor-El escaped while being captive. He takes three guys using only a flash as the distraction. Jor-El is pretty bad-ass and this scene was kept for a reason - to clear your specific doubt. Jor-El was very skilled at fighting but not as good as Zod.

I don't agree with you, he did not completely demolish Zod. Zod was just down for a minute and the launch was done. It was unfair really. Two against one. One working the launch and one fighting Zod.

Agreed, Zod was born and raised to be a warrior. While Jor-El was an intellectual. No matter what one is born to be, a drastic situation creates a warrior out of every being. Jor-El required drastic measures to evade capture and fight the general. While Zod was reluctant and more focused on the retrieval of the codex. He had respect for Jor-El and did not want to defeat or kill him. His purpose was to try and persuade Jor-El to agree with his vision. At the end, when the codex was sent to Earth, Zod finally killed Jor-El. Just because Zod was beaten a few times, it does not make him weak. Zod could easily have sent a few soldiers to retrieve, or taken some support with him. But he went in alone knowing the risk and the requirement of the situation for some tact.

Jor-El is a military scientist most likely and Jor-El in Superman: The Animated Series also kicked a fair amount of ass.

Someone needs to learn something new. Zod stabbed Jor-El in the stomach, but a few seconds later, he was launched skin dead into POD to the earth. Zod did only dismantled him a little. In a small village on earth, Kal el gets there as a superhuman. It is the good friend of Zod who killed him before he gets his superpowers activated on earth. Kal el wants to save his father. But since Jor-El forbids himself to get forever life he dies in his son's bloody arms. But his mother survives so thas something else. Yeiii?

In other series and movies, Kal El kills all bad before they get superhuman. Jor-el said they must wear power armors to take the sun down into a red giant. And after Kal El gets sent to death by a blue knife in the stomach all over again like his father was stabbed on his home planet before he leaves. Zod gets drowned into red chamber and Kal El kills Zod and his son easily. Kal El turns on a fake red light and Zod goes inside and thinks Kal El has lost his powers. He says kneel for Zod. But Kal El holds his hand and say no and then banish him to bottom of fortress. Zod has not learned all about how the fortress work and so on.

(Some words can be hard to write down in US English language so bear with me.)

Smallville 9x07 Clark interrogates Tess / Jor-El dies in Clark's arms

Smallville 9x09 - Pandora - Clark vs Zod / Lois uses the Legion ring

In one scene they leave pretty clear that they where mates, probably in the army, he even had a tactical body armour. By the way he fights against Zod is clear he had military combat training, Zod probably are like many other superior officers who are bad at hand to hand combat training, and rely a lot in weapons.