Nikon has released formware updates for its Z series mirrorless cameras: Z7 II, Z6 II, Z7, Z6, Z5 and Z50. New firmwares promisses AF enhancements for each model. In addition, Z6 gets a Voidce Memo feature added.
You can find the details of the firmware here: https://www.nikonusa.com/en/nikon-products/mirrorless-cameras/firmware-updates/index.page
Here are the model specific download links: