Difference between ISO and CMM level:
CMM is a way to communicate capabilities, but ISO is way to communicate the procedure.
They are not essentially incompatible.
The Capability Maturity Model is a very particular way of classifying an organization's software development methods.
In a sure way, it tells how the quality of its software designs is likely to be repeated.
ISO-9000 process describe a (possibly) definite development procedure but give no indication of the likely quality of the designs or whether multiple software efforts are likely to generates software of similar quality.