This is a highly skewed way of evaluating a DC, by looking at overall team record which is influenced by offense and special teams.
I mean, if you lose a game 14-10 and the QB threw 4 picks and the kicker missed 2 FGs, is it really the DC's fault you lost the game when he held the other team to just 14 points?
You have to look at how the defense ranked during those years under Zimmmerman.............I will save you some time..........most years his defense ranked in the top 10 in both yards and points allowed.