best thing to do is to measure it out... Look up the dimensions of the zalman and find out what the dimensions are... however usually the heat sink will sit up higher than the ram so you shouldnt have a problem.. usually the only problem people have whith a bigger after market heat sink is that it wont fit in thier case.. I have never heard of someone having a problem with it blocking thier ram slots
Actually I've been reading the opposite about aftermarket heatsinks on LGA1156. I was looking at reviews for quite a few different models and alot of people mention them blocking or coming extremely close to the ram slots, as well as the case.
... take darkjuggalo's advice - you have the advantage of having the board 'in hand'; look around for the price range you're looking for, then start comparing size. NewEgg is a good place to go (assuming they carry all your 'candidates'), as they usually have a 'manufacturer's link', as well as a batch of photos posted; use the mfg's site to d/l a manual and dimensions; use the photos to judge 'where the mount is', relative to the body of the exchanger (most, but certainly not all, will be centered); if they can't be bothered to post dimensions for their products - you can't be bothered to send 'em a check for their product!
I am using the "Quiet" version of this cooler mounted on a GA P55-UD4P. It does not block any of the memory slots. The bottom of the cooler is slightly higher than the tops of the memory sticks. Memory with the high cooling fins (or whatever they call them) would slightly block some of the air flow to the CPU cooler if four sticks are installed.
The case width is more likely to be an issue. I use an Antec P182 and there is less than a inch of clearance from the side of the case to the top of the cooler.