here is a little more info.
the ZC and D16A1 share a lot of internal parts, like bearings, rings, gaskets, etc., however, there are some differences such as timing belt and camshaft gears - the D16A1 uses a completely different block, different head casting (valve train parts are interchangeable), different valve cover, different camshafts, different camshaft gears, different crankshaft pully, different crankshaft on some, different timing belt cover, different front mount, different intake manifold, different exhaust manifold, different throttle body and probably some others that i can't remember offhand - suffice to say, they are not the same and the D16A1 will not bolt directly into a 2nd gen CRX, 4th-5th gen Civic, ect...