I haven’t tried a zercher deadlift, but I don’t think zercher squats are really difficult at all. I had never done a zercher squat before, and the first time I tried them I hit an easy 405 single, when my back squat max was just over 500. From a leg strength/effort standpoint, and even from a balance standpoint, I find zerchers to be easier than front squats. They’re painful, but that doesn’t really matter.
Yes, Bugenhagen is crazy strong. I don’t know anything about this other guy.