or you can get get rid of the trigger zone and right click over the entity dynamic and go to bottom and change explodable when destroyed and set strentgh to 1.
or have the explodable when killed on set the whatever entity in mid air and do as above but change the spawn at start to spawn after delay and then do trigger zone player in zone activateused then put the entity name in the if use part then it should drop the entity when go in zone the strength is weak and the physics force should destroy the entity when hits floor and hence the explosion goes off
an unquenchable thirst for knowledge of game creation!!!