When you increase or decrease presence in one zone, that light has to go/come from somewhere. Ansel spreads those changes across the entire histogram so it affects the relative contrast in each other zone as little as possible --- rather than trying to contain the effect to nearby zones. That approach would result in an obvious and unpleasant change in contrast in neighboring zones, so you'd have to go tweak them... and then come back... (I tried it that way, it was really unpleasant to work with.)
My suggestion: Focus on using the zone adjusters to effect small changes rather than large ones. The film curve and exposure sliders can do some amazing things, even with extremely broken images. If there's a specific image you're having trouble with, feel free to email it to me and I'll take a look at it and see what I can come up with.