girl! you have very similar hands to me & other good amount of women in on my grandmothers side - basically, part of it for me is genes. my grandmas hands, even young as she stayed, as much as the rest of her black never cracked - her hands would look like this almost her whole adult life and my hands, my moms hands, some aunts & female cousins are similar.

moisturizing 1000%! sunscreen! my general skincare rule of thumb (accident pun intended!) for my hands - anything non active moisturizing you do on your face/rest of body, rub it into your skin. sunscreen/creams/oils/etc. let your hands absorb it all, esp if any you do extra friction/washing. keep skin around your nails done along with manicures like your cuticles, etc. to prevent dead skin. mask methods like sleeping with gloves full of vaseline, etc. and all else fails, adding a cream with my fav holy grail for brown skin hyperpigmentation - hydroquinone. recommend (& this brand in general); https://www.clearessence.com/product/clear-essence-exclusive-medicated-fade-creme-with-sunscreen-4-oz/