The statistical z-test returns #DIV/0! for the z-statistic and P-values. I notice that even the help page on the z-test has these #DIV/0! results in the screenshots.
For the Data > Statistics > Z-test function
Tested in:
Version: 7.0.0.3 (x64)
Build ID: 8061b3e9204bef6b321a21033174034a5e2ea88e
CPU threads: 2; OS: Windows 10.0 Build 18363; UI render: Skia/Raster; VCL: win
Locale: en-US (fr_FR); UI: en-US
Calc: CL
The help page also has this in 7.1.