Hi, I also know that you can get the results by dividing the two polynomials, but I also knew that the rule was to have the denominator of the form 1+ sum(coeff_i*z^-i, i=0:infinity) , so I fuigured it should be the same here, but in order to do that, you can't simplify the numerator by the necessary z^-3 to get a constant at the denominator, and you should separate the 4 at the nominator, or something like that... I let it go... because I decided it didn't respect that rule. I may be wrong...
Also, if Matlab is allowed, a decomposition in simple fractions would also be possible, but still long and too complicated by hand so I thought of this method as the simplest, no calculation involved...
I honestly don't know if what you applied is perfectly allowed, I have Z experience, but not that much ... It's good though that we get to review all methods...
Regards,
Tzushky