I've tried taming it with a 9 and 12 handling skill pawn but both of them say 0% chance.
9 and 12 Animals skill isn't a lot. With so much you'll have trouble taming mufallos.
It just rounds off from decimal chances to whole, so it might be 0.2% chance to 0%. The chance is still there, it just doesn't show the decimal.
It is possible, difficult, but possible.
You'll probably want to contain the thrumbo and place down a stockpile for food, it may take a long time to get it done. :)
Think of it like... 99% Difficulty prisoners, with really nice stats and traits.