If I know the unique chip id for my IMX8DX and the fuses for TrustZone OEM key and Normal World OEM key are not set (they are still in their default values i.e. 0x0), would the challenge/response mechanism to authenticate secure debug succeed if I send both the responses as 0x0?
Yes, it should be possible. Just note that response eFuses are writable only from LC OEM Open. After switching to LC OEM Closed, these eFuses are locked out.