What produces these amazing 3D structures in Tibet?
The terrain examples show some striking similarities to what is referred to in the United States as "Badlands" - a type of terrain formed by layered sedimentary strata of rock that is soft enough to be eroded by wind and water into recognizably similar features. For example, here is South Dakota Badlands National Park:



Anecdotally, I have seen similar terrain in numerous areas of the Western United States, some appearing almost identical to the examples in the question. Furthermore, as mentioned in the updated question, the terrain examples shown for Zanda County, Tibet, are also referred to as the "Earth Forest"; further research of this specific location indicates that it was likely formed by similar erosive processes acting on "sediment stratum [...] mainly composed by sandstone and clay", comparable to the processes forming the various areas of Badlands in the United States.