Serious question
But Zamasu only believes in Himself. It is also Canonically stated by Zamasu Himself that he is "intoxicated with Himself". So this is a very extreme form of narcissism. Zamasu loves Himself. Zamasu loves Zamasu. In turn, Zamasu also loves Zamasu. And that's fine!. The concept of romantic or sexual love between two individuals is one that is widely accepted and celebrated. However, the idea that someone loves themselves in a romantic or sexual way is a concept that is often confused or disliked. Oh those Zamases
Goku Black is Zamasu being in Goku's body which it's not the first time Goku had another dude inside of him non consensually. It sullies it, like how the Babari sullied their world with violence, and that arrogant Goku sullied this sacred ground by swinging his fists at a god. Mortals received the divine gift of intellect, the potential for wisdom, but they misuse it to destroy the beauty of creation. A discussion of Zamasu's question in Dragon Ball Super
Absolute Zamasu starts to dread his existence and presents himself to the Omni-King, detailing on his actions. Using his powers the Omni-King restores everything to the moment before Goku and Vegeta perish, humanity's last barrier. One day, when serving Future Gowasu tea, he found his master killed under the hands of a mysterious man. The stranger then reveals himself to be Zamasu, from another timeline. 
Blamasu
Zamasu himself sees the Supreme Kais of Universe 7 as being of a high pedigree from having defeated Majin Buu. In the anime, when he was fighting with Super Saiyan 2 Goku, he is shown to be able to carefully intercept his punches. I witness this world, this universe , and the truth of all things. That yields deeper understanding.
Zamasu
Zamasu is a character from the popular manga and anime series Dragon Ball Super, and whether or not it can be considered “gay” if he is in love with himself has been a subject of much debate. . 
Serious question
If Zamasu wanted to fuck himself, he’d be self sexual. If Zamasu wanted to fuck Goku Black and vice verse, would it make him simply gay?. .
Are Goku Black and Future Zamasu gay?
Another reason that Fused Zamasu's mortal side (Goku Black) mutated, is that Potara fusion is permanent for Kais, Zamasu, being an apprentice Supreme Kai (界王神, Kaiōshin) himself. Thus, the Potara fusion should've been temporary, but since Goku Black was a mortal, it had caused a mutation in the fusion. . 
Zamasu
Says the guy who over wanks a character that wanks to himself on a different body In short yes, Zamasu likes the boy puss and the green slug or in this case the rose dungus. .