  We stress that in models with constrained minimal flavor violation large
negative corrections to the flavor-changing Z-penguin amplitudes are excluded
by the precision measurements of the Z -> b anti-b pseudo observables performed
at LEP and SLC. The derived stringent range for the non-standard contribution
to the universal Inami-Lim function C leads to tight two-sided limits for the
branching ratios of all Z-penguin dominated flavor-changing K- and B-decays.
