Older version installing itself with Zoom Workplace present (Windows)

[MrJeff]

At our company we have many machines in which version 6.0.39959 is installed (64bit) and mysteriously after a coupe days version 5.17.34827 also shows itself installed in control panel.  However inside the directory for C:\program files\zoom\zoom 64-bit\ , the only file present is "CustomAction.dll"  .   Why is this version installing itself ?  We cannot figure out why.

I would really mind this happening except it will kick people off meetings why it decides to install itself.