It is good to really think what the zoo wants to teach? Many random trivia information about animals are not really that important.
Show, not tell is the key. Good signs have painted things they want to convey. Be it a woman fur coat made from 6 snow leopard skins, or a cross-section of the brush turkey nesting mound with heat waves coming from the rotting vegetation and the sun.
Berlin zoo for years had animal signs with rather high quality oil paintings. They always drew attention to the plates. I think one of the zoo staff was a hobby painter. Also, this created the image of the zoo as a cultural institution, not a cheap kids attraction. In contrast, these huge photo plates seem to be ignored by visitors, who are over-familiar with animal posters.
My minor surprise is why signs are not actually put inside exhibits? This is where visitors actually look. Some zoos have names of individual elephants or rhinos on the stalls, but little else. Second surprise is why there is no information near sitting banks, children playground or in the restaurant? This is where visitors spend most of the time and have free attention to read.
Multi-language plates, often in 4 languages, are common in European zoos.
Aquatis Lausanne had interesting signs about Sahel wildlife. The zoo is near France, and France has a large Arabian / North African community. Many people seemed interested in animals in connection to their home country.