Just to clarify, by nullify ones islam, do you mean that the act takes you out of the fold of islam? Shirk will do this and Ive also heard apostasy will do this. Ive also heard that Allah does not even look at sodomites. I heard that and read something similar in Quran I believe (almost sure but I wouldnt want to lie on the Quran). Also, are you asking if I believe that zina with a woman is the same sin as zina with a man? If so, I think that there is evidence to make a case for yes and no, especially if you take into consideration scholars opinions. Zina is defined as sex outside of that which your right hand posseses and sex with a woman you havent married or do not own as a slave with consent and sex with a man will fall under this category. However, it is possible for you to marry a woman or recieve consent, but you may never marry same sex, sodomy is forbidden, and so sex having to do with the anus and other uncleanly practices. So if two men do that, i think they may be charged with zina, sodomy, and haram sex practices. I could be wrong though and Im willing to learn.