Hi !!!
Generally I love flower-themed names.
However
Zinnia has a screeching, fussy, austere and cold sound.
I think it's because of the two 'i' and the double 'n' that make it so severe to my ears.
I much prefer
Zayna with a similar sound. It's much warmer and gentle than it.
Personal Name Lists
https://www.behindthename.com/pnl/125456