I'm pretty sure you don't need that beefy of an FPGA board to accomplish this; there are cheap chinese Artix A7 100T boards with 100,000LUTs, almost 512k of block RAM, and 256MB of DDR3 RAM available for under $100 USD; I doubt a Z80 core would take more than a couple thousand LUTs.
For my own project I have a PicoRV32 RISC-V core running at 150mhz, with HDMI output, character set generator, sprite graphics generator, bitmap graphics output, and a UART all in under 8000 LUTs...
> As I’ve mentioned before, all of the logic so far is
> pretty lightweight, occupying a mere 7% of on-chip
> logic resources
The author is well aware the board is overkill. He also mentions elsewhere he used it because he happened to have it on hand, not because it's a particularly good fit.
For my own project I have a PicoRV32 RISC-V core running at 150mhz, with HDMI output, character set generator, sprite graphics generator, bitmap graphics output, and a UART all in under 8000 LUTs...