Yeah, this was very sad to hear. Zack's daughter committed suicide at the age of 20. My prayers are with his family.
The filming was more or less done on JL, so I don't know how much Joss will influence the finished product. (He's conducting some re-shoots) Frankly, I can't say I was a big fan of Snyder's 2 Superman films, but at the same time I wasn't too fond of Whedon's Age of Ultron either, so we'll see how it goes.