Zeiss and ASML currently have no competitors in the EUV lithography space as everyone else dropped out. (There was a big switch from lenses to mirrors)
I won't rule out a direct competitor, but they have a substantial moat.
They face some pressure from indirect competition like Canon Nanoimprint though.
Another way of framing your opening is "a bunch of other companies are on the verge of figuring this out, but the market isn't big enough". EUV hasn't even been the done thing for all that long, I gather it is only the tech of choice for about a decade.
There are a bunch of thin bottlenecks and oligopolies in global supply chains. It is a big and complex world. But that leads to a situation where three things are true at once:
* There are companies that are expensive to replace.
* No single company is truly irreplaceable.
* On the cutting edge, it is common enough for there to be only one company that knows how to do something.
I won't rule out a direct competitor, but they have a substantial moat.
They face some pressure from indirect competition like Canon Nanoimprint though.