Procede
I am aware of the El Al but did not include it as although it lost two engines the accident was not caused by insufficient thrust to remain airborne. They accelerated and raised the flaps and in the 747 when the flaps are up the outboard ailerons are locked out. The combination of damage to the lift devices on the wing and lock out of outboard ailerons led to a loss of roll control.
I agree that all 4 engines can be knocked out by something like volcanic ash. However I reiterate that no 4 engine jet airliner to my knowledge has been lost by continuing after an engine failure and having a further loss of engine power.