Index of row number minus row index of last non-zero element in dataframe

Using Python, I am trying to compute the interval between non-zero values in a dataframe, and input the interval as an integer in a dataframe. The following is a sample dataset:

Week	X	Y	Z
One	0	3	4
Two	1	1	2
Three	2	0	0
Four	0	0	3
Five	4	1	0

The following are the conditions for the output:

1. If value == 0, return 0
2. If value != 0, row number of value minus the last non-zero element

The desired output is this:

Week	X	Y	Z
One	0	0	0
Two	0	1	1
Three	1	0	0
Four	0	0	2
Five	2	3	0

I have tried using for loop and if else, but have always met with some form of error as my python proficiency level isn't high. Hope for some guidance here. Thanks!