User blog comment:Miskos3/Fairy Tail Chapter 486: The Fourth Guest, Review/@comment-6401212-20160524052444/@comment-7418318-20160524165314

So Zeref created a being that is a manifestation of his curse? That does sound interesting.

Considering how he didn't exactly like those 400 years he was stuck with the curse it's extremely likely that Zeref put some (probably considerable) effort into researching his condition at some point. While he obviously wasn't successfull in curing or breaking the curse, that research might well have yielded other, unforseen benefits which may have resulted in or been utilized in Bradman's creation.