Pentax 645Z has a Pentax 645AF2 lens mount and currently there are 6 native lenses available for this mount.
Pentax 645Z doesn't have a sensor based image stabilization system but 2 of these lenses already comes with optical image stabilization.
Since Pentax 645Z has a Medium format sensor, it has a focal length multiplier of 0.8× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on 645Z.
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Pentax 645Z Lenses with Image Stabilization
Pentax 645Z Lenses with Weather Sealings