Zero-sum games get more complicated when you care about the other players.

>there can not be shared interest between business owners and Unions.

There absolutely can. The point of a zero-sum game is that one party cannot win more without the other winning less. This is only a problem if all parties care exclusively about winning the most, rather than about winning enough sustainably. If you value your workers and care about them and want them to have happy, good lives, then you can absolutely find an alliance with a union.

It's not like a criminal justice case where one side has to win and the other has to lose, it's like a divorce where if everyone maintains a level head and allows the existence of humanity in the other side, everyone can come out happy. It only becomes adversarial when one side decides to make it that way.