[Balooga]

There are differences between the NMOS and CMOS implementations of the Z80. And an FPGA is neither NMOS or CMOS [1].

This is an interesting post describing the hoops one has to jump through to replicate an NMOS chip in an FPGA [2].

[1] https://sinclair.wiki.zxnet.co.uk/wiki/Z80#Differences_betwe...

[2] https://baltazarstudios.com/z80-ground/