What can I do to my hyperpigmented feet from years in the sun? (Photos)

I have tried a lot moisturizers, creams, urea, exfoliating every day , scrubs, retin A. I had tried everything applying on them for years now its been 4 years since and no change no improvement. Please help My feet are way darker than my body with line of demarcation a my ankle. I used to have white feet before.

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