The question is, can it be fixed? OP seems to feel it can't be, or at least not much.
I read years ago that Kehoe would test prospects by having then kneel while trying to keep their heels flat on the ground. As I understood what he was doing, was testing natural flexibility in the legs. I don't know how much of this is a problem of flexibility, strength, technique or a combination. Some people are naturally very tight. I remember that the NFL team that had Jarrett Payton on their roster tried to put him through a special flexibility program since he was very tight, especially, I think, in his hamstrings.
I think there's only so much you can do to enhance flexibility.
Maybe Zion will have to eventually move to the right side.