Apparently there is a PRC smear campaign against Adrian Zenz - https://www.mandiant.com/resources/blog/pro-prc-information-operations-campaign-haienergy, including by creating what Mandiant describes as what they "suspect to be at least three fabricated letters based on obvious grammatical errors and typos" to smear him - so I'd take anything that is ad hominem attacks against him rather than debating his actual work with a grain of salt.

However, even if you don't accept his writings, there are plenty of other people who have done credible research into the plight of the Uyghur people - e.g. resources contributed to https://xjdp.aspi.org.au/, such as articles like this one by Gene A. Bunin: https://livingotherwise.com/2021/01/04/the-elephant-in-the-xuar-ii-brand-new-prisons-expanding-old-prisons-and-hundreds-of-thousands-new-inmates/.