Question: I know how to use events to detect when the mouse button is pressed, however, how do detect if a mouse button is currently held down? Note I am not asking how to get it from an event.

I have not tried anything apart from `SDL_GetMouseState(&x, &y);` however it seems to only return the X and Y position of the mouse.

Answer: 
The top-level `<Zoom>` component needs a `key` attribute as well.
You should write `key` in `<Zoom />` component rather than in `<CardMedia />` like this

`<Zoom key={index} />`

Note: Always write key to first item component/element you are rendering here it is `<Zoom />`.