What do you call a person who can write with both hands at the same time?

There isn't a specific, widely used term for someone who can write with both hands at the same time.

However, you could use some descriptive terms:

* Ambidextrous writer: This clearly indicates the ability to write with both hands.

* Bilateral writer: This emphasizes the use of both sides of the body.

* Dual-hand writer: A more formal and technical term.

Ultimately, the best term depends on the context and your desired level of formality.