Zenith is not a private company! They were a public company that did not trade on any exchange. They now trade OTC.

DM's comment was because Zenith did not promote or arrange for trading on the OTC. It was done without Zenith's request or application which can obviously be done on the OTC. Because of the dismal price there, Zenith probably doesn't want to appear to support it but that is all he has said is that it isn't trading there due to Zenith.

There are many companies that have basically gone under but the company is still alive, barely. They don't qualify for respectable exchanges so if you still had shares in them, they would probably end up there. They might be worth fractions of a penny per share. Theoretically, you couldn't write off the loss because they still trade. If you wanted to write them off, you are supposed to try sell them there for what you can get or gift them then you can claim the loss.