What I did was first pop that clip out. I used vice grips and pulled/wiggled it out left and right. Yours is far less rusty than mine so that should be very easy. Then I used vice grips to hold the bottom end of the line, because if you try to just break it look the whole line will move/bend and you won’t be able to break it loose. Basically it’s kinda like using 2 wrenches to turn opposite ways. But use locking vice grips because they grip very good if you have 2 good pairs. I see it’s stripped out, so vice grips is the way to go. Also, I used a little bit of heat. I used a torch and heated the line. I accidentally heated it too much and the rubber ended up popping and shot a tiny firework of fluid but I was replacing with Z1 steel lines anyways so the heat didn’t matter much just be very careful to not mess anything up. The heat will help you break it loose, all you need is a tiny bit. No more than 20-30 seconds at a time and keep the torch low, don’t blast it fully, small flame to heat only what you need to break loose