To divide 900,000 by 1,000 it might be easier to write it as a fraction:
After doing this, you can cross out the same number of zeros on the numerator and denominator. Since there are three zeros in the denominator, cross out three on the top and bottom. MAKE SURE YOU DON'T CROSS OUT MORE THAN THREE ZEROS IN THE TOP! Always cross out the smallest number of zeros. Also keep in mind that this is only for zeros, not any other number.
Also, there are multiple ways to divide this number but this is one of the easiest ways (other than plugging it in a calculator).