How Does One Paint Isometry?

The usual drawing order is
1
2 3
4 5 6
7 8
9

But then tile 5 will overlap sprite moving between cells 2 and 3

And you can't draw underlying tiles before the sprites, otherwise large sprites would mess the higher level tiles. Typical tile cubes in games like X-Com and Magic & Mayhem are 32x32x16 (allows modelling nice curved terrain), while sprites are several times higher to maintain proportions

>>7

sort all drawn objects by distance to the camera

that is the same painter algorithm, which "can fail in some cases, including cyclic overlap or piercing polygons."