Two episodes with Zecora in a row. Nice. Maybe the writers, as I, thought that she hadn't been around for such a long time that she deserves the extra screen time.
And a whole episode full of Fluttershy. Sweeeeeeet!

OK, some throughs while watching:

- How can Zecora possibly not know about those flowers? She seems to know those flash bees, she's pretty much a herbal witch at home in the place, she knows about poison joke, but not about what those blue flowers can do that are floating around, falling from trees?

- Fluttershy being out of breath from running to the castle... Why didn't she just fly? Is she really faster on hoof than flying?

- When she presented the situation to Twilight, it was probably just to not waste episode time and because miscommunication wasn't a tool of the plot, but to me as a communication buff it is always a joy to witness right-to-the-point talk like that, haha. She might have picked that up from Pinkie Pie.

- They were so worried about Zecora coughing bubbiles, but I don't find that so bad. Ask Pinkie Pie what she thinks about this.

- I kinda expected that Zecora would eventually lose her ability to rhyme, heh. Those weird blue flower diseases like to shake things up massively.

- The two 'Fluttershy door puzzles' in a row were kinda hilarious.

All those technical points aside, the message of this episode was very dear to me. ( And it was a Fluttershy episode! Always a huge plus!  )
She cares so much for others that she can through cases like this enter an extreme imbalance that helps no one. After all, maybe the information about the mask WAS there in the book all along, as visualized, but she was too tired to make the connection. Then again...
What was a bit of the usual odd writing though was that in three days our smart pony Twilight couldn't figure out a solution. (But these maneuvers are kinda common in writing, actually.)

Another closely related lesson of the episode is that when you obsess too much over something, your mind blocks itself from utilizing things like intuition and calm observation. Sometimes you just gotta sleep over it to see more clearly.