Zeus Assembler is an assembler development tool for the Z80 originally written by Neil Mottershead for the Nascom 2 and then ported to the ZX Spectrum by Neil Mottershead and Simon Brattel in 1983. It was published by Crystal Computing. The program was designed to make Z80 machine code programming easier, with full symbolic instructions, and an editing style similar to the Spectrum's built-in BASIC.Zeus Assembler was later re-released by the manufacturer of the ZX Spectrum, Sinclair Research.