All zack snyder great commentary about superman and superheroes myth in general
Listen to Zack himself discuss that his intention, beginning with Man of Steel, to place the Superman character in the real world that you and I inhabit: https://www.youtube.com/watch?v=EOJj2zw2goM&feature=youtu.be&t=5m30s
Here is the salient quote: "I never felt like a [superhero] movie should exist in the real world before, but I feel like Superman should... All the Superman movies that have been made exist in some weird stylized world where everyone's, like, apple pie and Chevrolet and it's like the American Dream in a weird way... [T]he thing I find interesting is being able to release the character from that world, where he's been stuck and shackled, and bring him to our world and see what he does."
From https://www.forbes.com/sites/markhughes/2014/04/17/exclusive-interview-with-zack-snyder-director-of-batman-vs-superman/#4dd1d84a7bf4
"I think with Superman we have this opportunity to place this icon within the sort of real world we live in. And I think that, honestly, the thing I was surprised about in response to Superman was how everyone clings to the Christopher Reeve version of Superman, you know? How tightly they cling to those ideas, not really the comic book version but more the movie version... If you really analyze the comic book version of Superman, he's killed, he's done all the things-- I guess the rules that people associate with Superman in the movie world are not the rules that really apply to him in the comic book world, because those rules are different. He's done all the things and more that we've shown him doing, right? It's just funny to see people really taking it personally... because I made him real, you know, I made him feel, or made consequences [in] the world. I felt like, it was the same thing in Watchmen. We really wanted to show it wasn't just like they thought, like the PG-13 version where everyone just gets up and they're fine. I really wanted to show the violence is real, people get killed or get hurt, and it's not fun or funny. And I guess for me, it was like I wanted a hero in Superman that was a real hero and sort of reflected the world we live in now..."
And see https://web.archive.org/web/20160321191554/https://blogs.wsj.com/speakeasy/2016/03/21/zack-snyder-on-how-batman-v-superman-is-like-watchmen/ regarding the influence of Watchmen on this project of real world deconstruction in BvS in particular:
"I was surprised with the fervency of the defense of the concept of Superman. I feel like they were taking it personally that I was trying to grow up their character...
“[Alan Moore's 'Watchmen' is] ... all about the ‘why’ of superheroes: the political why, the religious why, the philosophical why... Once you’ve absorbed that material [of 'Watchmen'], there’s no way it doesn’t resonate with you, especially when you’re dealing with characters like Batman and Superman and Wonder Woman, who are basically the trinity. In some ways, this will be, I hope at it’s really best, the impossible version of ‘Watchmen’.”
Zack also explains in another interview that he regards Superman as, essentially, representative of all of superhero mythology itself. And he also further discusses the influence of Watchmen in his approach to Superman. See https://www.youtube.com/watch?v=EOJj2zw2goM&feature=youtu.be&t=3m10s