Hi there...as you know diabetics are prone to balanoposthitis and fissures over the prepuce. The uncontrolled sugar levels make to skin more prone to inflammation and injury. So unless your sugar levels are under control, the lesions will keep on happening. There's no two ways about it. Also surfaz tz cream you are applying is not helping the situation, as it contains steroid. It will only exacerbate the situation, especially since you have used it for such long duration. Do not use any soaps or antiseptics to wash your genitals. Only use lukewarm water with little salt. Only plain antifungal creams like miconazole should be used for few weeks and oral fluconazole can be taken of it is severe. If the condition is recurring, you can get circumcision done(surgeons will do it). Also get your wife tested for any white discharge per vagina. Both you and your wife must be treated. Kindly consult a dermatologist for further evaluation and starting treatment.