\firstchapteris{N>}before the
\dominitoc
and analogous commands. N> is the number
of your first chapter. This command does not
modify the numbering of chapters, you must use a
\addtocounter{chapter}{-1}
command to get a first chapter
numbered 0. The \firstpartis
and \firstsectionis
commands are analogous for parts and sections with a non standard numbering.