How do Zookeepers communicate with them? Any Elephant whisperer/expert/other person, who can tell me?
Hand signals and body language.
A training reinforcer such as a clicker.
There are other training methods, some of which may be illegal where you live. Use of a bullhook is illegal where I live (Los Angeles).
Elephants are awful smart animals, doesn’t take long for them to know their keeper/handlers intentions.
Wild elephants are not to sure what to make of humans so don’t make it obvious you might be a threat.
They can be trained. In fact, they are smarter than dogs.