Try to make your search as simple as possible:
Zehneria will find all items including that sequence of letters.
Search results for "Zehneria":
"Zehneria macrocarpa" - Trochomeria macrocarpa
"Zehneria scabra" - Melothria scabra Cucamelon / Mouse Melon
"Zehneria umbellata" - Solena umbellata