Glad it was of help! There's certainly more to it than what I posted, as Absolome described. But someone should definitely try to compile an updated guide/tutorial while the game's popularity is still running high from AGDQ. Information is a little scattered right now and it might be a turn off for new runners. The GDQ tutorial is a decent starting place, but I can see people getting annoyed that higher level runners are doing different tricks and there's not really a good place to learn them without reinventing the wheel.

Looks like you aren't pressing left to break out of the zip before you're forced back out of the wall, as far as I can tell from the input display. Try pressing and holding left as your sprite is starting to wrap from the top of the screen to the bottom.

I also noticed that holding right for too long after unpausing seems to make it impossible to break out of the zip in time.

Take this with a grain of salt as I just started playing after the tutorial, so I may have no idea what I'm talking about. But hopefully this is better than nothing.

I managed to pull it off a few times on FCEUX at reduced play speed. Here's a recording of it at 10% speed (note: there is an input display on bottom left):

And here is an explanation of the inputs I used along with some visual cues: https://imgur.com/a/UJTDh

Hope this helps; or at least gets people to start finding out and documenting what does and doesn't work.

Edit: The term "wall jump" is definitely a misnomer for this trick, as the inputs have nothing in common with the kind of wall jump that was done on Red Dragon before the new jump skip was found. This a lot more similar to a normal zip, only way less lenient.

Edit 2: Got it in real time. So here is another example to work with: Also confirmed from that the inputs are the same regardless of rather you get the crouched to the right pose or the knee up to the left pose after turning left in the wall.