Based on the complexity of your schema, you could do this either through direct map or custom xslt. I am not very good at custom XSLT. But if you can describe your schemas for both message types, you can get quick responses from XSLT experts in this forum.
HTH,
Please mark it as answer by clicking on "Propose As Answer", if it helps
HTH,
Please mark it as answer by clicking on "Propose As Answer", if it helps