Saturday, November 7, 2026 · Customer reviews of US businesses
The Fair Hearing score
Great
95 reviews
Z-STACKSelect a line to read only those reviews.
Honesty, pricing, process and quality scores appear once 5 customers have rated them.
Zelenko Labs, built on the legacy of Dr. Vladimir Zelenko, creates products with purpose, precision, and integrity. Every formulation is made with high-quality ingredients and consistent standards, so you can feel confident in what you’re using. Thoughtful, reliable, and principled — Zelenko Labs products are made for people who care about quality.Our All American customer service team is here to help Monday through Friday, 9 AM to 5 PM EST — just give us a call at 1-800-ZELENKO (1-800-935-3656) or email our team at [email protected]
Z-STACK (zstacklife.com) has 95 customer reviews on The Fair Hearing, with an average rating of 4.1 out of 5.
Showing 71 reviews with 5 stars · Clear filters
I have been taking Z-Stack for years. I know without s doubt it has helped me fight off colds and other ailments. Several years ago, I got COVID, even after taking 3 sticks(never again) but with all the ingredients in Z-Stack, it was like having a mild cold and it was gone in days. I WILL ALWAYS use Z-Stack as I do believe in the founding father and now the company. Jeff
By JLL
Response from Z-STACK· Jul 1, 2026
Thank you!
I have been taking Z-Stack since COVID. I am 70+ years old and I have not had any illness. I even went to Mexico the end of Oct/Nov 2020 with no issues. I highly recommend this product. I have made other International trips in the last few years and faithfully take Z-Stack.
By PATRICIA G.
When I contacted Shannon from Zelenko labs about my missing shipment, she immediately replaced it with another one. I greatly appreciate the value they see in their customers and vice versa.
By Matthew B.
I have taken Z Stack since 2021 and have not had a sick day in the time since. Never got Covid. Very good immune protection. (I added K2 to the regimen some time thereafter due to learning that this is needed with the D3 to redirect calcium from the arteries.) Dr Zelenco has passed, but his legacy continues on with this great formula Z Stack.
By Anonymous
Response from Z-STACK· Jun 24, 2026
Thank you!
I have been on this product since 2022 and have not had a sick day since
By RavenRebel R.
Response from Z-STACK· Jun 24, 2026
Thank you!
For three years Z-Stack ihas been an exceptional preventive against bacteria and virus both - takes me literally 15 minute to break an attack. It also seems to prevent Covid 19. No side effects at all except good health. Most grateful to Dr. Z.
By Hugh H.
Response from Z-STACK· Jun 11, 2026
Thank you Hugh!
On-line customer service was excellent. Responded to me in less than 2 hours. Issue was resolved quickly an efficiently. BEST customer service I have ever recieved.
By Fern M.
Kindness expressed Willingness to pause delivery schedule
By Anita
Response from Z-STACK· Jun 3, 2026
Thank you Anita, anytime!
