What happens if two or more effects would cause a library to be shuffled simultaneously?

When two or more effects in Magic: The Gathering cause a library to be shuffled at the same time, the abilities that trigger from this event will each trigger separately for each shuffle effect. This means that if a library is shuffled multiple times due to different effects, the trigger for shuffling will occur for each of those effects.

When an ability refers to the library being shuffled and triggers on that event, each instance of the shuffle is recognized as an independent event, leading to multiple triggers. This aligns with how Magic: The Gathering handles simultaneous events; each effect is processed in a way that adheres to the rules, allowing all related triggers to happen as intended.

Thus, the correct answer reflects the mechanics of multiple simultaneous shuffles resulting in multiple instances of triggered abilities being activated accordingly.