You have to consider the following :
1) in your honest opinion, how did you perform in the interview ?
2) how many other candidates got zero marks ? What was the total number of candidates against posts available ?
3) check interview marks against the academic marks of the Candidates. Do you see a reasonable pattern or do you find an inverse relationship - high academics and low interview - which would be unreasonable and illogical.
4) how has the pattern been in previous years ?
If posts were limited and many candidates scored above 60 in academics but got zero in interview then your case is weaker since only way to eliminate such candidates would be to give them zero in interview.
of course there would be a strong defense and you have to proced carefully.