Mazda ZY and Z6 Engine Question

[Maestrolujan]

Hi. I have a ford focus 1.6 that needs an enginr change. My challenge is i wanna downgrade a bit to a 1.4 or a 1.5. Been told there's not much difference between a Z6 and ZY engine. How true is that? Will it be safe to buy a ZY engine and install it in the car? If so, what do i need to change