E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Se trouver entre le zist ct le zest. To be in a quandary; in a state of perfect bewilderment. Also, to shilly shally. Zest is anything of no value, as Cela ne vaut pas un zest (It is not worth a fig). Zist is the same word slightly varied.