Lets suppose this dataframe, which I want to filter in such a way I iterate from the last index backwards until I find two consecutive 'a' = 0. Once that happens, the rest of the dataframe (including both zeros) shall be filtered:

```
    a
1   6.5
2   0
3   0
4   4.0
5   0
6   3.2

```

Desired result:

```
    a
4   4.0
5   0
6   3.2

```

My initial idea was ussing `apply` for filtering, and inside the apply function using `shift(1) == 0 & shift(2) == 0`, but based of that I could filter each row individually, but not returning false for the remaining rows after the double zero is found unless I use a global variable or something nasty like that.

Any smart way of doing this?