Painful rash may suggest zona but the distribution of this rash is not quite an indication of zone. Zona usually hold one dermatome. It is not diffuse over the skin.
It doesn't seem like shingle because it isn't in dermatom and not vesicular . I suspect skin malignancy or PIH (after contact dermatitis). I suggest skin biopsy.
It s not a zona looks like a kaposi sarcoma. Stand up to biopsies and if there an immunodeficiency notion or a recent pulmonary disease. Look at nodes areas.