Yeah as said the should be all the same for a ZS but a lot of people advertise any K series 1.8 as 'fits MGF/ZR/ZS etc' Which is true. The differences between the earlier MEMS 1.9 (pre 2001) 1.8's are the presence of a distributor and lack of a cam phase sensor and oil temp sensor. They also use a 4 wire IVAC and have the MAP sensor integrated into the ECU.
If you want to buy an early one just fit your cam carrier (for Phase Sensor), inlet manifold (for MAP + IVAC) and oil filter housing (for oil temp). You can leave the dirtibutor off and pull the drive peg out. Use the mems 3 water temps sensors aswell.