Useful Zilog Z80 coding and optimization resources

Z80 ASM Optimization Tricks - v2.1 (by Adam Ziemba, 2006)

Z80 Optimization Technies v1.1 (by Christopher Tremblay, 2000),

Z80 instruction set

Twitter bot for BASIC and Assembler programming online:

How to Write Spectrum Games v1.1 (by Jonathan Cauldwell):

First Steps in Z80 Assembly Language v1.2.4 (by Darryl Sloan): + YouTube (4 videos)

Z80 Assembly Language Subroutines (by Lance A. Leventhal and Winthrop Saville, 1983):

The ZX-Spectrum screen layout: part 1 + part 2 + part 3

Z80 Optimisation Tricks

8 videos - Z80 Assembly Language for the ZX Spectrum Tutorial

3 video lessons - Learn Z80 Assembly 2021 Edition

several video lessons - Zilog Z80 Part X

Offline tools

SjASMPlus, command line z80 assembler: download + documentation

Online tools

Z80 assembler, disassembler, hex/dec/bin convertor, ZX spectrum emulator in browser: