Zoe debuted in 1992, the year they switched taping studios and the year they started using that crazy Calypso opening theme and the current closing credits. "Around the Corner" didn't come until a year later.
Also, unlike other newer commonly-seen Muppets, Zoe is performed by one of the original Muppeteers from the show's early years; Fran Brill. Then again, she's the youngest of the original Muppeteers (and Frank Oz is the second youngest), so I can see why she's still working with the show.