What if these two had an interaction?

it’d probably go something like,

shrek: GET OUTA MEH SWAMP YE PURPLE BRAT
jack: do you know who i am insolent green bastard? *fires unicorn horn*
donkey: *jumps in front of shrek to protect him*
shrek: DONKEH NOOOOOO!!!! you’ll pay for that!

fight seen

shrek on the ground multiple magic wounds: i’ll tell you one more time, GET OUTAH MAH SWAAAAAAAAAAAMP *charges knocks jack too the ground*
jack firing magic between every word: WHY *magic* WONT *magic* YOU *magic* DIE?
shrek: i’m the main character I HAVE PLOT ARMOR! *kills jack and brings donkey back to life with his tears or something*

well that was fun

Nah it would go like this: jack was only nine years old. Jack loved Shrek so much, Jack had all the merchandise and movies. Jack would pray to Shrek every night before he go to bed, thanking for the life he have been given. "Shrek is love", Jack would say, "Shrek is life". Father soldier hears me and calls me a maggot. He knew soldier was just jealous for his devotion of Shrek. Jack called him a maggot. He slaps Jack and sends him to go to sleep. Jack is crying now and his face hurts. He lays in bed and it's really cold. A warmth is moving towards him. He feels something touch him. It's Shrek. He is so happy. He whispers in Jack's ear, "This is my swamp". He grabs Jack with his powerful ogre hands, and puts him on my hands and knees. Jack spreads his ass-cheeks for Shrek. He penetrates Jack's butthole. It hurts so much, but he'd do it for Shrek. Jack can feel his butt tearing as his eyes start to water. Jack pushes against his force. He want to please Shrek. He roars a mighty roar, as he fills Jack's butt with his love. Father soldier walks in. Shrek looks him straight in the eye, and says, "It's all ogre now. MAGGOT!!!". Shrek leaves through Jack's window. Shrek is love. Shrek is life

wtf?

In terms of magic, Jack would most likely win, but if it were just a plain old fight, no weapons or anything, Shrek would mop the floor with him.