It would be easier for God to have allowed the donkey and the snake to telepathically communicate with the humans, so completely that the humans would PERCEIVE it as sound waves entering their ears, instead of thoughts entering their minds.
But, hey, we both shall agree with your claim that all things are possible with God.
Fun part of that is: If God exists, then it is possible that the Bible contains plain facts, exaggerated facts, misunderstandings, fictional stories, accidental errors, deliberate lies, forgeries, good advice, bad advice, bloody awful advice, and some really nice poetry.
You're the one saying all things are possible; I'm just pointing out that if you're right, it's possible that the Bible is wrong.
The people who actually wrote down what the snake and the donkey are reported to have said, were not physically present at the event.