I agree with a lot of those that said Zero Year dragged on but I don't know where exactly Snyder could have cut his story to make it flow better; it's pretty clear to me that this should have been an OGN or something that wasn't released over 12 months because many of the finer details were things I had completely forgotten by the time the payoff came around. I really didn't like Zero Year at all (while I've enjoyed pretty much everything else Snyder has done on Batman) because I thought it was either showing me things relating to other things I had forgotten about or showing me things that weren't interesting enough in the context it was presented for me to call back to it when I was supposed to; like those little images put at the openings of those early issues (I imagine if I go back, it'll make sense and have a pretty good meaning but I shouldn't have to go back to them).
My biggest problem with it though was that Snyder was trying to modernize the themes in Year One while also trying to modernize the story and I don't think those two things can be done together (or I don't think he pulled it off at least). Year One was so perfect for me because it so effectively established an atmosphere and tone that fit so well with Batman. It defined Gotham in that story and it defined it for the stories that followed too (including the ones told by Snyder) and while doing this, it paralleled New York in the 70s. Snyder was trying to show that his Batman was facing modern fears in a modern day New York-Gotham but the Gotham in modern Batman comics is still that 70s New York from Year One. The city he showed in Zero Year felt completely different than the one in almost any Batman comic being published; it also seems like Gotham got way worse (and I mean significantly worse) between Zero Year and current day so I think that aspect doesn't fit with the fact that this is an origin.
Just overall, Year One was way better for me. I think if I re-read Zero Year in one go, I'll probably like it more.