With Combine ZM all you do is:
1) Chose 'File'
2) Choose 'New'
3) Select your photos in order (top to bottom)
4) Choose 'Do Stack'
And that’s it
The process makes an out-of-focus border that needs to be cropped
You can take charge of each step if you want but that looks far to complicated to me
At installation Remember to tell it how much Ram you want it to use or it might otherwise be a bit slow
Peter