1.6 zetec to 1.8 zetec? or cvh to zetec?

if both are zetecs then all you need is the engine and the ecu. you should be able to mate it to all your ancilliaries as the blocks are the same, then bolt the old inlet manifold and exhaust on to it, plug all your existing loom into it and just put the new ecu where the old one was.

if the old one was a cvh then basically, get the engine mount too and fitting it all in should be straightforward. the wiring just needs to be replicated what was in the old engine bay, where the loom is disconnected from the donor car, you'll need to connect it to a fuel pump relay, ignition relay and then a couple of fuses and it's just ignition live and permanent lives.