I want to produce the following output:
Notice - this is multiline, the equations are at the center of the page. There's alignment w.r.t. the inequality sign, and even though there's a large size difference in each side between the upper and lower terms, the shorter term (12) is aligned at the center w.r.t. the longer one (123456789).
Every solution I've tried aligns the shorter text to the left or the right. I've read many related questions and have spent many hours attempting to solve this, without any success.
eqparbox
package. See my answer to vertically-aligned-text-in-math.