Blue Islands is the only realistic option of finding a new operator to fly to Zurich. It is just like the Isle of Man route, based primarily on a thin but lucrative business market.
I don’t see any other airline that could operate to Zurich. VLM and, more recently, Atlantic Express have considered operating to Zurich but nothing has ever come of it. These airlines have the resources to operate the route though they choose not to, which I think emphasises the very limited appeal of a Zurich flight.
It is also positive that Guernsey is using their initiative by offering route development funds. I can see the potential with Dublin and possibly destinations like Cardiff, Edinburgh or Glasgow.