On another note, I am extremely interested to see how the sex between Zack and Sophie starts and how the seduction progresses because Sophie looks like a tough nut to crack.
She has been portrayed as a very loving, very supportive wife. The good thing about this is that it will make the NTR really good once it starts. However, the bad side of it is, if it's not handled carefully, the NTR will lose all of its power very quickly.
In NTR, when the FMC is shown to be loyal and truly in love with her partner, three general rules have to be followed for the NTR to work:
1. It has to be slow. (Boil that frog, baby.)
2. It has to be consistent with her character. (ie. You can't make her a bitch to the MC out of nowhere without laying the groundwork for it.)
3. It has to be believable. (...within the context of the story, at least.)
Hopefully the Dev can pull it off. I really like the story so far, so I'm rooting for him.