Many of you, like me, have been trying to do the trick on the Shocktrooper involving Jean, Geo Traveler, Tighnari, and Zhongli. There are videos out there that do a good job explaining the technique. (The only minor modification I made in my own runs was hopping backward and just a hair to the right after using Traveler's skill, instead of stepping backward with Jean, as I felt this gave me more control over positioning).

I struggled for many hours (probably 7 or more) trying to get it, and I couldn't even get STARTED on properly trapping the dude. He received one tick of damage maximum, and then he would just get pushed out from between the constructs.

It turns out there IS a trick that makes it significantly easier to succeed.

It is this: Check your FPS. If it is set to 30, set it to at least 45.

I don't know why, but after doing this, the guy actually started getting stuck between the constructs and I succeeded in like 10 minutes. This might not help everyone succeed, as there are numerous things that can go wrong when attempting this strategy, but I hope I help at least someone.
Tip for those attempting the Jean fall damage strategy in Stygian Onslaught!!