RCD Live and Neutral Protection
If all of the shock current flows between live and neutral then there is nothing the RCD can do. It does not know that the load it is presented with is a human body rather than a peice of electrical equipment.

However it is worth noting that the most dangerous shocks are those that pass through the core of your body. Unless you do something really stupid like grabbiing the live with one hand and the neutral with the other, live to neutral shocks are most likely to be limited to an extremity, whereas live to earth shocks have a much greater chance of passing through the core of your body.