let me break down what that's doing. It will make it easier to modify to fit your needs.
VBASTMT tells acad that you want to enter a vba command at the command line
thisdrawing.SendCommand basically the same as (command in lisp)
"sh rename " & The first part of the command string, the & tells it to add the next part to the string
ThisDrawing.GetVariable("dwgprefix") & Gets the path of the drawing, substitute the path to your zip
Left(ThisDrawing.Name, Len(ThisDrawing.Name) - 4) & gets the drawing name and strips the .dwg off
".bak CAD-" & Adds a different extention to the filename and CAD- to the new filename I meant to change this to .zip but was testing with .bak
Left(ThisDrawing.Name, Len(ThisDrawing.Name) - 4) & Again, drawing name without .dwg
".bak" & again, meant to use .zip
vbCr Enter so the command will execute
The net effect of all of that is somthing like
VBASTMT
Enter Expression: sh
OS Command: rename c:\drawings\here\drawing.zip CAD-drawing.zip
Command: