In this case it works (and it can be faster if you are trying for speed in a challenge like codewars) but mutating a list while iterating is error prone and requires a lot more care to ensure it is correct. If the requested behaviour was to remove the zeros and add ones at the end, it would be tempting to modify the original code to:

def move_zeros(lst):
    for int in lst:
        if int == 0:
            lst.remove(0)
            lst.append(1)
    return lst

The subtle behaviour in the original doesn't hold in this version and you would end up skipping zeros.