The Zercher Squat (ZS) is probably one of the most hated squat variations there are. It is uncomfortable to do, difficult to set up for if you don't have a power rack, and downright miserable if you go too heavy. All that aside, it's an amazing addition to any squat program!
Take a look at the following video to see the "classic" setup, i.e., without a power rack, as well as a couple reps.
The Zercher Squat will take some time to get used too, but the effort is worth the benefits you will reap from it. NOTE: if you look closely you will see that the Zercher Squat closely resembles the kettlebell Goblet Squat. If it doesn't, you might want to work on it a little more!