Tapping a Nazgûl to access a sideboard

[Konrad Klar]

Tapping a Nazgûl to bring cards in from the sideboard does not turn the Nazgûl into a
short-event. It is discarded immediately upon declaration.

Annotation 5: If an action requires an entity to tap as a condition for the action’s main effect, that entity must be untapped when the action is declared; else, the action may not be declared. Tap the entity at this point; this is considered synonymous with the action’s declaration; i.e., it is not a separate action. When it comes time to resolve the action in its chain of effects, that entity must still be in play and tapped or the action is canceled.

So at the first glance it looks like the action is self-fizzling.

Other possibility: active condition of the action is joint "tap and discard". In this case Annotation 5 does not apply.
But it has other consequences.

[...]
Nazgûl permanent-events that are targeted by Praise to Elbereth may not be tapped in response to its play.

So if condition of the action is joint "tap and discard" and not just "tap" the action may be declared in response to Praise to Elbereth (using a Nazgûl that is a target of Praise to Elbereth).

Other ideas?