I like your ship idea a lot. It looks to me like there was a base hull that over the years had a lot of additions organically welded on and a lot of repairs made.
But, the shader you use looks much too plastic for me to find this believable. Specifically, it looks like a rather small piece of plastic when given the scale I feel the ship is rather meant to be enormous. If this is supposed to be a metal ship (which I suspect from the color) I would make the shader more metallic (decrease roughness to sharpen specular highlights, and possibly increase reflectivity depending how much you like chrome). Maybe also add some rusty patches and small scratches, rivets all over. If it is supposed to be an organic ship I would take some inspiration from an old whale's skin, a lot of small surface details and long scratch scars, etc. You have ZBrush, you should be able to paint some nice base color.
Basically this is very nice but the shader and lack of tiny surface details is taking away a lot from the sense of size.