If column a=0, then use column b, if column b=0, then use column c

I have 4 columns (A-D) and a fifth column (E) I want to have a valid value.

My logic for E2 is something like "if D2 is 0, then use C2, and if C2 is also 0, then use B2, and if B2 is again 0, then use A2" Then i tried this formula: = if(D2=0, C2, if(C2=0, B2,if(B2=0, A2), D2) sure it won't work..

Please help here! Thank you!