We seem to have strayed from daylily terms beginning with Z to cultivars beginning with Z. Not surprising since there aren't many terms beginning with Z, the only one in the Daylily Dictionary is zygote:
https://daylilies.org/daylily-...
There aren't many in my plant terminology dictionary (Harris & Harris) either, just:
Zonate (marked or colored in circular rings or zones
Zoophilous (animal-pollinated)
Zygomorphic (bilaterally symmetrical
