''Pretty much every single New Testament scholar and Islamic scholar recognises there is a vast theological/symbolism/spiritual language in a large chunk of both Books. ''
There is of course allegory and symbolism in both books, but what you claim depends on what exactly you are referring to and which 'large chunks of both books' you actually mean.
If you mean that the return of Jesus is meant to be a spiritual event, then that is not what the first generation Christians believed. They fully expected the literal return of Jesus, come to usher in the Kingdom of Heaven on Earth, for all the World to see, to judge mankind, etc, as described. That is what they believed would happen and that precisely reflected in their writings.
