What is the difference between these two words?

Create - bring (something) into existence.
Discover - become aware of (a fact or situation).\

The crux of this difference is choice.

Imagine a painter and a map-maker both dispatched across an unexplored country, Lewis and Clark style.

The painter takes inspiration from the things they see, and creates paintings. They choose colors and perspectives, and which scenes to highlight.

The map maker takes measurements and carefully traces them into their notebook.

Did they create or did they discover? The map maker created a map, the painter created paintings. But we might say that the map maker made a mistake if their map does not accurately describe what they went out to see, and we can say the painter made a mistake if their painting does not represent the scenes encountered.

We cannot say for certain that they discovered a certain area unless they accurately represented it.

So too would I say that math is partially created and partially discovered. Our equations and notations are created, and the things that we are attempting to represent are discovered.

The collatz conjecture is either true or false. Fermat’s last theorem is true. The Goldbach conjecture is either true or false. There is no choice in these matters. These are discoveries.

Logic seems to be persistent in all space and time and outside of it as well. With any given consistent set of axioms, we may only discover what can be proved with those. These facts would be true using our language or an alien language, or whether we were in our universe or outside of it.