for part d you must set z^6 -1 equal to one and then find a root the e.g 1
you must then use (z-1) as a root and if that is a root so is its complex conjuate (z+1) you must then use this to form your quadratic factor. Also for complex polynomial it has exactly the same amount of factors as its degree.e.g. six does this help??
for part c is it asking to solve seperately or at once.