It’s not really 3D
It’s literary all in JavaScript, under the mit license and it’s really light.
I kinda like it.
Could it run under GDevelop like PixiJS, YarnEditor and the other js stuff? What do you think?
GDevelop is not going to be a 3d engine Afaik (yes also not pseudo 3d).
Zdig has man problems. The first being that you need to create models using code, meaning that every model has to be created by hand (you cannot use an existing one because it is not compatible), and cannot be exported because importing them would be a security flaw (as it is code that would be executed to be imported, anybody could put the code of a virus in it). That would also mean we would have to create a full 3d model editor, and that is not an easy task. At all.
Second problem: it is lightweight, but this has the cost of not being very flexible. It could probably not do all what GDevelop can do with “normal 2D”.
Animating would also not be possible if we don’t create a full animation library for that renderer.
And finally, it has some bugs and the fact that models have a problem with z order that can’t be fixed because of the way it works.
I understand, thank you for the explanation. 
I can create these pseudo 3d models using only events. But it is difficult for them to find practical application, since problems with Z-order remain.
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