stamen
橤 centers on the stamen, the pollen-bearing part of a flower. It is a specialized botanical character with no common abstract extensions.
橤 combines 惢 (a triple-heart shape, likely phonetic) with 木 (tree/plant), suggesting a plant part. The exact historical development is uncertain.
The top 惢 looks like three hearts hanging down, and the bottom 木 is a tree. Imagine a tree with many tiny heart-shaped stamens dangling from its flowers.
For ズイ, picture a bee buzzing around the stamens: the buzz sound 'zui' cues ズイ as the bee collects pollen.