How the relation between Issuer and Verifier works? How does Verifier get to know the zkProof submitted by the user for verification is created through credential issued by trusted Issuer?

This is part of the query, there is a field that is called “allowedIssuer” when you add this symbol means that you allow any possible issuer can create a credential. In case you want to select a specific issuer you need to add the DID that the issuer has if you want to issue a credential.