pistil, stamen
蘂 centers on the reproductive parts of a flower: the pistil and stamen. It refers specifically to these botanical structures.
蘂 is a variant form of 蕊. It combines the plant radical 艹 with 橤, which likely contributes the sound and the idea of clustered stamens or pistils.
The grass top 艹 sits above a complex lower part that looks like multiple hearts (心) hanging from a tree (木). Picture the delicate pistils and stamens of a flower clustered together like tiny hanging hearts.
For ズイ, imagine a bee buzzing 'zwee' as it lands right on the pistil: zwee -> ズイ, and the bee pollinates the flower.