Looks like Blue Diamond's voice actress is Lisa Hannigan now! A quick Google reveals she's an Irish singer/songwriter. Crossing fingers for Blue Diamond song later in the series?
Yeah, The Zoo was a really interesting episode! I really liked the inhabitants and their carefree, childlike personalities. Really curious to see what will become of them now that they have been introduced to the concepts of pain and "choosening" for oneself. Probably wouldn't be too much of a leap to go from that to questioning other aspects of how they live. Zoo rebellion maybe?
Also, I've seen others point out that there's a shot of the inhabitants' grasping hands that strongly resembles the grasping hands on the mural in the Pyramid Temple. Not sure what that means yet other than that the zoo was foreshadowed, but regardless it seems noteworthy.