Sum values in a row until a new value appears (Right to left)

I have been looking everywhere and can't find what I need.

For instance, I have these columns:
A B C D E F G
0 3 4 0 0 0 0
2 2 5 3 2 1 0

What I would like to count (backwards) is how many times does 0 show up. So, in the first row, it should give me 4 and in row 2 it should give me 1.
I want the formula to stop once it finds a different value than 0. I was thinking of a COUNTIF, but I don't know how to make it from right to left and to make it stop once it is different than 0.

Thanks in advance for your help.

Thank you Sambo kid, but this would give me 5 in the first row and it should only be 4, as from D to G the values are 0.
It should stop counting after it encounters the 4 in column C

Exactly, if in the most right column there is no 0, then it shouldn't count or just return 0.
Sorry, my explanation wasn't very clear

Try this?

=IF(G1=0,IF(F1=0,IF(E1=0,IF(D1=0,IF(C1=0,IF(B1=0,IF(A1=0,7,6),5),4),3),2),1),0)