I just ran a quick check with lz4 on one of the ROM images in the latest release of ROMWBW (EZ280.std.rom), and got a reduction from 524288 to 276020 bytes at the highest compression level. That might bring the time down to 15 seconds or so.
That’s an interesting observation. I have used unarj.com in CP/M and arj.exe in Windows to compress and decompress files. I tried arj.exe on ROMWBW for ZRC (RCZ80_ZRC.ROM) and achieve significant reduction in file size, from 512K to 240K. Something to think about…
Bill