Congratulations! It must be so rewarding to finally get flowers after you have cared for the tree from its infancy!
I am happy to have bought a replacement 3gallon black sapote for one that got taken out by disease, and found that even though it is small yet, it pushed flowers! I have yet to transplant the plant so the flowers will have to go if they don't drop of their own accord, to help the plant adjust to its new location, but it's a great feeling to have a black sapote that one knows is capable of producing. These were several individual, separated flowers, so they should have been theoretically viable.
It was really nice to see a black sapote flower in person, as my last tree was older and larger than this one, but had not flowered yet that I had ever seen. (I had it in the ground for about a year and a half, and it was one of the healthiest plants I had in my yard up until it got struck, so I feel like I put in my work to see some flowers by now!
) They're pretty little yellow and green sort of trumpet-shaped flowers. Unfortunately, I forget now which variety I ended up buying - I ended up just picking the healthiest-looking plant - but it may have been Bernicker or Reineke?