The zinc for the common cold review by Singh and Das has a number of problems which should be considered when the review is next time updated

In 2011, Harri Hemilä found that there were severe errors in the Cochrane review “Zinc for the common cold”. He wrote a feedback in which he encouraged the authors to correct the flaws, which is this document. However, when the next version was published in 2013, Hemilä found that essentially all errors remained. In addition, he found out that there was unattributed copying of text and data from another report, see details [1]. Thus, the editors of the Cochrane Acute Respiratory Infections group did not check that the flaws demonstrated in 2011 were corrected. They just pasted the feedback to the 2013 version of the review. Eventually, this process ended with the withdrawal of the zinc review [2],

The parallel JAMA Clinical Evidence Synopsis by Das and Singh (2014) was retracted in 2016, see doi: 10.1001/jama.2016.18134.

1. Hemilä H. Concerns about unattributed copying of text and data, and about numerous other problems in the Cochrane review “Zinc for the Common Cold” by Singh M, Das RR (2013). 2015. 
https://hdl.handle.net/10138/153180 
https://doi.org/10.5281/zenodo.6394115  

2. Singh M, Das RR. WITHDRAWN: Zinc for the common cold. Cochrane Database Syst Rev. 2015 Apr 30;2015(4):CD001364. 
https://doi.org/10.1002/14651858.cd001364.pub5
https://www.ncbi.nlm.nih.gov/pmc/articles/pmc6457799