Black-bellied starling (Notopholia corusca corusca) - Animalium BRIN

Subspecies from along the coast of Eastern Africa, from the Horn of Africa to South Africa as well as Eswatini and the Zanzibar Archipelago (Except Pemba Island).

Edit: After referencing more sources, this bird turns out to be of an Lamprotornis species, still not sure which. Sorry for the wrong ID.

True black-bellied starling appears to had never been exported outside of their range.

I think this is neither Notopholia nor Lamprotornis, but rather Aplonis

@ralph I was able to go again to get more clearer view of the bird. There are some Aplonis indeed in the same walkthrough aviary, but this single bird is clearly a lot larger and a bit more metallic blue than what some Aplonis usually looks.

The bird appears to be an Lamprotornis chalybaeus. Here's the much clearer photo I took of it.
Species Gallery - Southern greater blue-eared starling