As I mentioned, this combo has
technically existed for a while, however nobody played it (to my knowledge) because it was too slow (a turn 6 Goldfish isn't very good) and required an all-in deckbuilding approach. Thanks to Zirda, however, we only have to commit 5 mainboard cards to the combo, and the activation costs are more efficient so we don't spend an entire turn activating Staff and doing nothing else.
A big addition to the deck is Myth Realized. It does a number of things: first, it applies pressure. It isn't blisteringly fast, but it does provide a clock. It's also relatively safe from removal, so you can wait to animate it until you've used hand disruption. Another sweet benefit is that Zirda's passive ability affects Myth's mana sink: instead of Zirda being dead without Proteus Staff, she can be helpful by making a big myth. Finally, in a pinch, you can animate Myth and hit it with Proteus Staff to do the same combo as with Zirda, it will just be a little more mana intensive.
Lingering Souls is another great addition, for many of the same reasons as Myth. Souls give a clock, slow down our opponent, or give an alternate target for Staff to combo with.
Supreme Verdict is one of the strongest boardwipes in modern, and we pack them in to stop our opponent's creatures. Spot removal like Path and Push help in the early turns, but a well-timed wrath can ruin any aggro's day.
Academy Ruins gives our artifacts some resiliency. If Belcher gets blown up, discarded, or milled, Ruins puts it right back where it belongs.
Another advantage of going Esper is the hand disruption package we find in Inquisition of Kozilek+Thoughtseize. Preemptively stopping our opponent's game plan or picking off removal to clear the way for Zirda is vital.
