I think you should not botter with such question, you love your dog and its the main point, having him a breed will make no difference in how good pet he is already for you.
You will waste your money with DNA tests which will be used for nothing than your own knowledge, it will not change your dog at all as well as shouldn't change your relationship with him.
If nor even you, that is the owner, knows the breed of your own dog, then he simply have no breed, maybe he have some blood of CzW, maybe not, maybe he is a pure CzW, maybe not, it will make no difference.
Enjoy your dog.
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