Ukrainian military managed to invade Russian land. Hundred thousands of Russians had to be evacuated. Russia managed to defeat the powerful Nazi army, against military from all Europe. But can't defeat the tiny Ukrainian army. This looks so fake that is unfuckingbelievable.
The armies of all EU countries are strong united, but none of them are designed for invasion of a foreign nation, they're great for defense only.
This is why the cold war stayed cold for so long, and still is cold. Neither side has the resources required to conquest the other, and both sides have decent defense in case of war between EU and Russia. If the US and China gets involved as allies it makes very little difference and would most likely result in small border conflicts in Europe while the US and China fights a full scale war on the other side of the world.
But if they were wearing ukro uniforms they could be considered volunteers or mercs.