The 120mm macro Mamiya lens is my sharpest lens (sharper at close focusing distance than my 150mm f2.8 and 120mm Schneider T/S).
Tested with an IQ180, tethered and with many, many iterations of focus bracketing.
Maybe the Zeiss is even sharper, don't know, but the 120mm Mamiya macro is already so good that it's a rather cheap must have anyway.