Not trying to burst your bubble, but it's not a hybrid with anything.
It's simply a drake mallard with some genetic issues. I've seen it numerous times, and it's quite common with park mallards, and other ducks with limited genetic diversity.....not that your duck is a park duck.
Some things to remember about hybrid waterfowl:
When a mallard breeds with another bird, the offspring will always display more of the other birds characteristics over the mallard's.
ie: a brewer's duck - mallard/gadwall always has the bill shape and head structure of a gadwall and secondary coverts, primary coverts, and speculum will be much more like a gadwall's.
a mule duck - mallard/pintail always has the blueish bill and head shape of a pintail, and many of the secondary coverts and speculum are pintail driven rather than mallard.
It's the same with members of the mallard complex as well.
Down here in South Carolina we get many mallard/black duck hybrids, but also mallard/mottled duck hybrids along the coast.
The birds always look more black duck, or mottled duck than mallard.
Also, outside of the mallard complex, hybrid waterfowl are sterile. For example, if a mallard breeds with a gadwall hen, their offspring will be sterile, just like a mule horse. They cannot produce children.
Mallards, blacks, mexican ducks, and mottleds can and do produce fertile hybrid offspring, because they are so genetically close and they derive from a direct common ancestor. It's likely that the mallard was the initial bird, and the others evolved to seperate subspecies.
Hope this helps.
teal and tailing reds make life worth living