Quagga: Did they go extinct or are they still with us?

The last quagga died in the Amsterdam Zoo on 12 August 1883. 

Yet by selective breeding they have returned. 

The Quagga Project

The trick is the quagga were not a separate species. They are Burchell's zebras with a distinct color variation. While arguably a subspecies, the genes still existed in zebra populations.  

Smithsonian: Quagga: The Lost Zebra

AoSHQ: Morning Report 08.12.19