Zero Hour is very much not worth reading. It has some interesting tie-ins, but the miniseries itself is very bland and complicated.
But I think you’re conflating 52 and Countdown. 52 is more of an epilogue to Infinite Crisis. It’s a bit convoluted, but entirely self-contained within the series itself. No wonky reading orders or anything, just fifty-two issues of awesome. Countdown is the Final Crisis lead-in with seven billion tie-ins that contain more plot than the actual series. They’re easy to get mixed up because Countdown tried to piggyback on 52’s success by using the same cover design and starting at issue #51 and counting back down to 1 just after 52 counted up from 1-52 (the titles are pretty indicative, though). Their actual plots have very little to do with each other. I would only recommend 52 to someone with a strong working knowledge of DC continuity, not because the plot doesn’t hold up on its own but because the writers are all continuity junkies who like to throw in lots of little nods to obscure old characters and stories (Rucka maybe a little less so than Waid, Johns, and Morrison), and they’re all going full blast through the whole thing.
Also, Knightfall is a bit of an acquired taste and has a ton of padding in the middle, but I like it. No Man’s Land is maybe not as coherent taken as a whole, but has more entertainment value from issue-to-issue. Both of them are a little intimidating, though. I’d recommend them more to hardcore Batman fans than to general DC fans.