What should I do after I committed Zina with a girl whom I later discovered to be a "shemale" (a male who has transitioned to a female)?

Error occurs due to leniency and lack of firmness, which leads to falling into the trap of Satan. Allah Almighty says: "O Children of Adam, let not Satan tempt you as he removed your parents from Paradise, stripping them of their clothing to show them their private parts. Indeed, he sees you, he and his tribe, from where you do not see them. Indeed, We have made the devils allies of those who do not believe." You have committed two sins: indecency and informing your companion about it. You must repent to Allah for both of them. And you must learn from this lesson to strive for righteousness and avoid the causes of temptation.