A simple shape like a cross might be possible, but for something like a dragon, depending on the degree of wrap, in ZBrush Core you will need to sculpt it in that pose. Even in the full version of ZBrush which has far more robust mesh editing and deforming tools, this might be a little tricky. ZBrush Core is an introductory sculpting app, and sculpting a shape should be the first resort.
For something like a cross, it would be easier to simply create the mesh in the pose you want it to begin with. This can be done with Subtool >Extract. Mask the portion of the target mesh you want to extract, then this function can be used to extrude a new mesh from that masking as a new subtool, which can then be further refined and shaped. The curvature would match perfectly. The resolution of the target mesh along with the extract settings impact the quality of the extract.
You could also use the Extract function to block out the rough form of a dragon wrapped around the target mesh, then further sculpt it into shape. You’d be starting with a mesh that was already wrapped in the pose that you want, and then begin refining and detailing.
Otherwise, the best option in ZBrush Core for attempting to make one existing mesh conform to another is probably the Gizmo Deformer Soft deformer option. You can use masking to isolate control points to affect soft transformations. This might be adequate for conforming a simple mesh to a somewhat curved surface, but it would be difficult to wrap a mesh fully around another with this.
The full version of ZBrush would provide you with far more options for what you’re trying to do.