Let Z be the number of 8-digit numbers with 8 different digits, none of which is 0. How many 8 digit numbers exist that are divisible by 9, that have 8 different digits, none of which is 0. Answer in terms of Z. 

I tried putting in 9, also tried putting in 18 at the end but soon realized that only some numbers with these endings will be divisible by 9, not all.