Unfortunately after consulting my Lynx rodents book, I'd have to say these are likely to be Brazilian porcupine (Coendou prehensilis), as bicolored-spined porcupine (Coendou bicolor) look like this:
Really confused why the zoo went with the labeling it did (was listed this way on ISIS back in the day as well) as it would seem to be impossible to confuse the two species, and one is common in zoos and the other isn't.
It seems there's a bit of variation in C. bicolor and some do look more like at least the animal in the back but I wouldn't be surprised if they were both C. prehensilis. I always assumed at least the animal in the foreground was but I was unsure about the second animal.
@ThylacineAlive But even the shape of the body and how the spines on the back half of C. bicolor seem to usually be much smaller unlike these animals. And the coloration for C. prehensilis can vary as well to include some yellowish. Did you have any other photos showing more of the animal in the back?
They are both prehensilis. The "bicoloured-spined" of the name refers to the quills being pale at the base (white or yellow) and then black. In prehensilis the spines are tri-coloured - pale at the base, then black, and then white at the ends.
However, this zoo was listing on ISIS (back when it was publicly available) as holding both species so I guess that they have simply retained the signage for bicolor.
