ZnO thin films are deposited widely by RF magnetron sputtering, along with the doped zinc oxides. However to determine the exact deposition parameters, either you have to develop your own recipe or to refer to already developed recipes from literature. This is because the process includes many different factors such as: the RF power, Argon and oxygen gas flows, pressure and temperature, even the type of substrate.

check this paper, It would help

It is very easy to deposit ZnO film by sputtering techniques.

RF sputtering a preferred method.

and depending upon the power you can cah achieve good deposition rate, and achieve ZnO film growth with a preferred (002) orientation on simple substrates such glass, oxidised silicon, silicon, and metallized silicon substrates.

The sputtering pressure and Ar/O2 ratio should be carefully chosen.

A sputtering pressure of 20 to 30 mTorr, and

60% oxygen (AR+O2) sputtering gas mixtures would do the job.

Many poeple try to optimise the sputtering pressure and the argon to oxygen ratio so that they have low residual stress in the films.

K. Sreenivas 

I work a lot in ZnO sputtering, however I am not familiar with piezoeletric.  So what I can suggest you that, first you need to know what kind of ZnO properties you want (defects, roughness, conductivity/resistivity, crystallinity, orientation of the crystals either prefered 002 or not, etc.). Then, based on the literatures, you can start to find the best recipe for your needs. It may takes some times, but it is the only way.

Piezoelectric ZnO films deposition was the subject of my PhD thesis. I successfully applied both DC and RF sputtering. So I can say that any of the parameters listed in the articles is related to the specific plant. You should read the articles, take the average values and to optimize the process for your sputtering system. And you will see, that there is nothing difficult.