d16a6 is like the single cam ZC.
and yes that block is better... but the D16z6 head is better (VTEC)
a friend of mine works for bullfrog, he has a ZC with a Z6 and stroked it to 1.8L 12.6 all motor all day.
ZC is japanese version of the d16a6. D16A8 IS A ZC. they are the exact same block. If your asking us this question for a swap, pick one you can find for cheap and do it. but they are all relatively the same. if any, barely any hp/tq difference to notice.