In my parts it takes 3-4 months on average to be processed and dealt with. I do my tax form in February, and by June I get my final decision back. I guess I’m lucky!

For the next tax year, keep in mind that in ZH you can simply underpay your provisional tax bill if you already know it's too high (or ask them to adjust the provisional bill). If you've overpaid, it is normally not possible to get anything back before the final tax bill, though. If you've paid too little you have to pay interest but that's only 0.25% p.a. at the moment (Ausgleichszins).

Here in NE canton, I received my return the following year (usually between Oct-Dec) every year.

For 2019 though it seems to be delayed. No word yet. I imagine it may be covid-related delays but not sure.

As an update to my post: I emailed the Zurich Tax Office and received the reply that they are still working on the 2018 tax refunds and that they should start looking at the 2019 assessments in Q3/4 of 2021.

Jeez - gonna be waiting a while for my 2020 refund then