Too many strong roots...
 

Here is a video of my fighting my Zygo. I hope I did the right thing in not touching the roots and just working around them. I put it in a larger pot but just filled in the space around the Root Brick.

What do you do with a plant this root bound with healthy roots?

zygopetalum ROOTS!!! - YouTube

With roots like that I would have put it into a much bigger pot, with a more open mix. Literally 4 times the size as those roots need space to move out.

To me the risk is that in a couple of years you will have a much bigger solid block, and at some point the core will go anoxic and start to rot.

You are obviously giving the plant what it likes in terms of conditions, because it is growing well.

That was the biggest pot I had. I will watch the roots and when they start moving to the edge of the pot I will look for another bigger pot.

I think a larger pot right now would cause rot. This pot has room for the roots to more just not much room for the new growth. I will make sure to repot it more often.