Upgrading a base model ZX Spectrum Next with Accelerator board, Wi-Fi and RAM.
Easy peasy, 10 minute plug and play upgrading of the ZX Spectrum Next with modules that can all be bought from one site: https://store.activeconsult.co.uk/
Software for the Pi 0 micro SD card can be obtained from: https://www.specnext.com/latestdistro/
Addendum: I incorrectly mention that adding the 2 extra 512kb RAM chips upgrades the Next TO 1mb RAM. It actually increases it BY 1mb RAM to 2mb in total.