If you want to write faster Z80 code, pretend it's a Game Boy, and use the IX/IY registers sparingly. You can use 256-byte aligned tables. Then you put your index into the low byte of the register pair, and which table into the high byte of the register pair. You don't even need to completely use the table if you don't need all 256 entries, you can treat the rest of a table as free space to put other variables in there.

edit: At the time I made the post, the thread title was something like "Doing Z80 40 years later", and did not mention the ZX spectrum.