Need help on my research!

1. We are introducing a new process in 2021 which might affect customer returns behavior. My data is in proportions which is total number of returns of total number of units sold. I need to test if there's a significant difference of returns/units sold in 2020 versus 2021 using the new process. Sample table below 

[![enter image description here][1]][1]


****Question, given this data is it true that I can use the Z-test Hypothesis testing comparing two proportions?****

2. In relation to question no. 1, what if Total Business is breakdown into different categories. LIke the table below. Basically this is just a breakdown of the total business. 

The objective is to test if there are significant difference in 2021 with new process in terms of category level. 

[![enter image description here][2]][2]

**Given this, is it safe to use the CHI-SQUARE TEST?**


  [1]: https://i.sstatic.net/0h2Bb.png
  [2]: https://i.sstatic.net/jLtfH.png