Pentax 645Z: Does Not Have EFC Shutter (Electronic First Curtain)
An electronic first curtain shutter (EFC shutter) is needed for vibration-free exposures.
According to Pentax, the Pentax 645Z does not have an electronic first curtain shutter. The 645z does have the same excellent mirror lockup feature as the 645D, and its shutter is generally well-damped (quite possibly no medium format camera has an EFC shutter). But a focal plane shutter is not and cannot be vibration free.
Like all DSLRs lacking an EFC shutter, longer lenses can be an issue: see Blur from the Shutter at 300mm in the review of the Pentax 645D.