A few years ago, there was a method/way to transfer Delta miles to Hilton points. Delta had Award codes as follows:
Z991 5,000 miles = 10,000 points
Z992 10,000 miles = 20,000 points
Z993 20,000 miles = 40,000 points
Z994 30,000 miles = 60,000 points
I transferred miles from my Delta Frequent Flyer account to my Hilton account a number of years ago. This may have been a one time only deal, but it was possible. And it may still be possible, ASK!