On page 109 of my book I referred to Eliyahu HaNavi as the only Human being who ascended to Heaven alive. At least 2 readers contacted me to point out that according to Chazal, there were numerous others besides Eliyahu HaNavi.
Here is how I responded to the last reader:
Firstly, thank you for your letter and thank you for reading my book. Believe it or not, you are not the first person to challenge me on that statement concerning Eliyahu HaNavi. My response earlier, and now as well, is that what I had in mind is that Eliyahu HaNavi is the only human being that is attested to explicitly in the pasuk to have ascended to heaven alive. All of the other tzadikkim mentioned in Derech Eretz Zuta are based on our mesora from Chazal and, with the possible exception of Chanoch, there is no firm basis in the Tanach.
Although we live and breathe the words of Chazal, we cannot always consider their statements to be conclusive because they are often subject to conflicting Midrashim or a range of opinions among Chazal themselves. To point out a few examples, on the same page I note that there are at least 3 opinions as to which shevet produced Eliyahu HaNavi. The contention that he is a Cohen and that he is Pinchas is compromised thereby. Also, see footnote 25 on page 102 where I bring conflicting sources as to which tzadikkim were born circumcized including a head-on collision concerning Bilaam. Another example is a controversy as to whether Zimri was actually Shlumiel ben Tzurishadai which contradicts a Midrash that all of the original nesiim died in the maaseh Korach (according to Rabbenu Bechaye). There are numerous other examples of this. It's true that I have not actually seen any dissenting opinions on the Derech Eretz Zuta, but still I was relying on what is undisputed in the pasuk.
Still, your point is 100% valid and duly registered.