Please go through these paper you will get all of your answers

http://cpb.iphy.ac.cn/fileup/PDF/2015-4-046104.pdf

https://ac.els-cdn.com/S0169433211003321/1-s2.0-S0169433211003321-main.pdf?_tid=44e83e3a-b188-11e7-8999-00000aab0f6b&acdnat=1508058629_1b82137b2f629e32fa13db71d97dc416

https://link.springer.com/content/pdf/10.1007%2Fs12043-007-0068-7.pdf

Dear Elmira,

in an Infrared absorption spectrum of ZnS one cannot find the peaks of Zn or the peaks of S, because one can only find the peaks of the vibrations of the bonds Zn-S. Moreover, it is fundamental knowing if your ZnS crystal has the bulk structure of blende (cubic) or the structure of wurtzite (hexagonal). Please, send me these important data that you can find through a X ray powder spectrum and then I could discuss with you about the infrared behavior of this interesting compound.

All the best

Dino Aquilano