After going through the website, which is not the clearest in regards to Lights before Christmas, I found a link to a map that had the following exhibits as fully closed:Those hours are bizarre. I cannot comment on how the darkness would affect your zoo visit, but since the indoor area of the zoo are the main part worth seeing I would think visiting now would be fine - the only outdoor exhibit worth seeing that you would miss out on in the winter would be the Pheasantry.
Flamingo Key, Cassowary Crossing, the Aviary, Pheasantry, Great Apes, Galapagos Gardens, Penguin Beach.
Partially closed are: the Promedica museum of natural history (Second Level closed), Primate Forest (Indoor viewing closed), Nature's neighborhood (Indoor viewing closed)
That is most of the zoo including many indoor areas and highlights. It is weird to see a northern zoo as big as Toledo essentially closed for the winter. I'm hoping to visit in the spring or summer instead. They still seem to be charging full admission which seems, frankly, quite ridiculous.