Has Izzy and Zipp ever considered being mechanics or engineers? They would make a living repairing machinery for big bucks, no need for detective work or crafting.
I enjoyed this episode, got some much-needed interactions between Izzy and Zipp and they work well together. I still prefer Izzy and Pipp together and there should be episodes where they both interact more.
Magitek has existed for a long time in Equestria, as seen with the airships in the G4 were likely magically powered through the side wings only seen on the ponies’ airships. The other realms’ airships were steam-powered or wind-powered with propellers and sails. So the Marestream can be considered a continuation of this, although the magic allows it to fly. From what the episode shows, the vehicle has a combination of pegasi and unicorn magic that allows it to fly with a spell similar to the one Starlight Glimmer had used.
And when the Marestream was built, a new discovery was learned; Zipp and Izzy teamed up to rebuild the tram, had been so fired up by the effort that the magic in them “got out of control”, manifesting through the cutie marks and being transferred to the Prisbeam lantern. This confirmed that the lantern draws magic from the ponies, specifically Izzy. The Crystal Heart drew magic from the crystal ponies when it was freely given, to create a shield and prevent evil forces from forcing their way into the Crystal City in the G4. We see this principle around the Prisbeam lantern.
Zipp and Izzy knew what they wanted, and the magic - the magic of their talent - was essential to transform the tram into the vehicle they had imagined with the help of Izzy’s design and Zipp’s technical know-how. And here lies the great discovery, the magic behind the cutie marks is much more than just talent and identity.
In fact, all magical beings have a “foci” to use active magic outside their own body. By understanding that magic is layered, so that active magic can be stored and removed in a magical world, it is possible to realize the importance of foci for intelligent magical beings who must be able to manipulate magic. We now know that the ponies have internal magic that didn’t disappear when the active magic was gone, they just can’t use it because the foci were “turned off”. Twilight had made sure of that.
A mystery in G5 is why there is only one cutie mark on the ponies where there were two, but the TYT episode may have provided an important pointer towards this. Because ponies have more than just natural foci (horns, wings, hooves), their cutie marks are advanced focal points with magic channeled through them. This may be why the cutie marks glow depending on mood and focus. Izzy had the Prisbeam lantern made, thus unknowingly creating a connection between it and the magic of the Mane 5. I see this being emotionally determined, like when Sunny was happy, determined, or desperate, or when Izzy and Zipp had a good time during their work.
The ponies have dual receptivity unlike any other being on Equus to “chain” their own internal magic with active magic and can manipulate magic. That could be why Misty couldn’t use magic, she hadn’t gotten the cutie mark and since she grew up when magic was gone, her natural foci were disabled as well. This is possibly what had made the ponies the strongest magical people in the entire world.
Hologram-Twilight is right, magic has evolved and gotten stronger. Not only because of the Unity Crystal, but also because the ponies’ own magic had evolved as a natural continuation of evolution. But the problem of emotional instability has not yet been solved. Twilight until Equestria’s collapse may have seen this long before Sunny was born and realize magic is constantly evolving.
So the Cutie mark is far more important than thought. So important that this is central to MYM/TYT.