The Inline Assembler permits to easily include machine code portions in a C source:

 int one_hundred()
 {
    #asm
    ld hl,100
    #endasm
 }

sccz80 features several extensions to C to enable mixing of C and assembler:

  return_c                - As return but sets carry flag
  return_nc               - As return but resets carry flag
  iferror{...} else {..}  - As "if { }" but checks carry flag
                            (does else {...} if nc )

The optimizer is active on the inline portions of code, too. To keep it unchanged it is suggested to export it in a pure assembler module and to link it into a library.