This citation can take several different forms, and I'll list several examples of what I've seen:
Some authorities, who have spent their entire lives studying the origins of names, believe that “Jesus” actually means— “Hail Zeus!” For Iesous in Greek is “Hail Zeus.” That is, “Ie” translates as “Hail” and “sous” or “sus” is Zeus. Dictionary of Christian Lore and Legend, J.C.J. Melford, 1983, p. 126.
"It is known that the Greek name endings with sus, seus, and sous were attached by the Greeks to names and geographical areas as means to give honour to their supreme deity, Zeus." -Dictionary of Christian Lore and Legend Professor J. C. J. Metford
"It is known that the Greek name endings with sus, seus, and sous which are phonetic pronunciations for the chief Greek god of Olympus - were attached by the Greeks to names and geographical areas as means to give honour to their supreme deity, Zeus." -Dictionary of Christian Lore and Legend by Professor J.C.J Melfurd (1983, pg 126)
Greek name suffixes transliterated as -sus, -seus and -sous are phonetic pronunciations for the chief Greek god of Olympus—Ζεύς. These suffixes were appended by the Greeks to names and geographical areas as a means to honor their supreme deity, Ζεύς. J.C.J Melfurd. (1983). Dictionary of Christian Lore and Legend. p. 126.
Some of these present themselves as quotes whereas others are summaries. One oddity we can see in these is disagreement on how the author's name is spelled; we can see them cited as Melford, Metford, or Melfurd. It is, for the record, Metford.
But we also run into the question of why we should trust this claim simply on the authority of J.C.J. Metford. You see, if his German Wikipedia page is correct (surprisingly, there is no English one), J.C.J. Metford appears to have been a professor of Spanish. Him writing up an encyclopedia of Christian terms already seems out of his area of expertise, much less making statements concerning the origin of Greek names. But honestly, even if Metford knew more about Greek name etymology than anyone else in the world, it ends up not mattering, because the claim made isn't in his work.
One can see page 126 of this work here on the Internet Archive, though you may need to sign up for a free account and check it out to view it, as otherwise only a few pages can be viewed. It was published in 1983, by J.C.J. Metford, and it has the same name as the work being cited. Thus we absolutely know this is the right source. But someone can notice something quite obvious if you look at page 126: The claim about how Greek names ending with sus, seus, or sous coming from Zeus is nowhere to be found. Heck, Zeus isn't mentioned at all on the page. A search for "Zeus" turns up a few matches, but none saying anything like the above. So the whole citation is false! The work doesn't say that!
So much for that claim. The text that supposedly supports this... doesn't. It doesn't say anything at all about names in Greek ending with sous/sus/seus coming from Zeus. Were people just too lazy to look up the source to verify it? It was uploaded onto the Internet Archive back in 2013, so it's been available there for quite some time. And even before it was made available there, it's not a rare book, and is in a ton of libraries on WorldCat. There are multiple libraries within twenty minutes of where I live that have it. This is not a difficult book to check. So the "quote" and related claims about Ditionary of Christian Lore and Legend is nonsense.
While this post was only concerned with this specific citation, I suppose I should include links to people responding more generally to the claim of the supposed link between the name Jesus and the name Zeus. See here, here, here, here, or here for responses to it from several different sources and viewpoints. (Note: This is not an endorsement in general of any of the websites I point to, only the specific linked pages)
So the lesson here, as is often the case, is not to just assume that a quote you see online is true. Here we have a bunch of people repeating this supposed claim from this work even though the work doesn't actually have it. All it would take is simply looking at this book (which is not actually that hard to get a copy of, to say nothing of the possibility of just looking at it online) to show it was false, but apparently none of the people who repeated this false claim bothered to do so.