Can I blend a block of marzipan (from Ikea) and a block of Neufchatel?
I don't know why you can't. You'd want to make sure they are both at room temperature. If either is cold, I'm sure it will be nightmarish.
Just out of curiosity, is this some diah from Switzerland?
No, I live in Michigan. Making treats for a ladies get-together: puff pastry squares, topped with the marzipan mix, topped with tart cherry preserves.