The ZY Optics Lens Turbo 2 is a 0.72x speed booster for M42, EF and F mount lenses on Nikon Z bodies
Viltrox Ef-z2 Auto Focus 0.71x Reducer Speed Booster Lens Adapter For Canon Ef Mount Lens To Nikon Z Mount Cameras Z6 Z7 Z50 - Lens Adapter - AliExpress
Viltrox EF-Z2 Speed Booster Allows Canon EF lenses Used on Nikon Z-mou
GEAR REVIEW: The Metabones Speed Booster for that Full-Frame Look Pt1