The credit rating of Zimbabwe is difficult to calculate, because of the lack of reliable data. Anyway, based on some proven data the result is D.

Generally the lack of national currency due to hyperinflation and the very new default (2006) is enough to crash entirely the rating...

Debt/GDP = 2,3 (230%)
Accumulated deficit for last 5 years/budget income for last 5 years - no reliable data
Years since last default = 6 (2006)
5-year inflation = more than 230 000 000%
Budget expences/GDP = No reliable data
Trade deficit/GDP = No relable data
Political factor = 0,3
Crisis factor = 0,5 (Economic disaster at home territory)

With so much lacking indicators it is not possible to calculate a rating. But it is possible to calculate that any possible rating will be below 50%. Therefore the credit rating of Zimbabwe is D.

OVERALL CREDIT SCORE: below 50%. This responds to D.