In my searches through Internet it appears that nobody, but nobody has got around to making a serious recording of "Zoological Gardens". I found this song, as you have already guessed, in good old Soodlum's 100 Irish Ballads Volume 1
(actually Soodlums should pay me for the number of times I've mentioned them!). The lyrics, as given in Soodlums, are full off double entendres and I find the song quite difficult to date. For example there are Transatlantic idioms such as "we had no dough", which sound like the twenties and thirties, contrasting with "...if you don't come soon" which sounds like the post-pill period (excuse me, but the alliteration is intended) starting in the middle sixties. Then we have the quaint phrase "I took the mot.." which I believe is pure Irish or pure Dublin. Perhaps some kind, erudite surfer could clue me in.
Any roud up, as one says in Birmingham (England and not Alabama), the song is great fun and one's fantasy runs riot over the line "..when Dublin City is in the dark" which is very reminiscent of our present modern times when complete power break-downs in major cities (like New York for instance and not only Dublin) are not unknown. However it is highly improbable to imagine that in New York the population of "hairy baboons" could increase resulting from a power-cut as the song suggests might happen in good old Dublin (blame it on the Guinness!).