x * y = z where x, y, and z are positive integers with x smaller than y. The combined digits of x,y,z includes each of the 10 digits exactly once.

What constraints are there on the magnitudes of x and y?
List all solutions for (x,y,z).

Bonus. For which two solutions is the sum (x+y) the same, and what is the value of that sum?

note: no leading zeros