Based on this I think I may be right, but I figured I should ask to be sure: Can I use a Zaiko's (already in play) entering-play Interrupt on an action that's not putting Zaiko into play in order to have it be negated by Shadowed Estate, so I can have it use the melee safely? If yes/no, under what circumstances can you use Interrupts that wouldn't affect the action being interrupted?
Zaiko and Shadowed Estate of the Scorpion
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Based on this I think I may be right, but I figured I should ask to be sure: Can I use a Zaiko's (already in play) entering-play Interrupt on an action that's not putting Zaiko into play in order to have it be negated by Shadowed Estate, so I can have it use the melee safely? If yes/no, under what circumstances can you use Interrupts that wouldn't affect the action being interrupted?
Yes, you may. For the most part, you can use an Interrupt on a card even when it will have no effect; in this case, it will use up the Shadowed Estate's negation.
On: Zaiko