To me they sound more like a mix between AC/DC and Aerosmith. If that is the same as Led Zeppelin in your book, than it's fine with me. You might as well say that all hard rock bands are Led Zeppelin clones.
Nope, there are - thankfully so - a lot of hard and heavy rock bands which are largely or totally Led Zep-content-free: Black Sabbath, Deep Purple, Uriah Heep, Golden Earring, Queensryche, Thin Lizzy, Ted Nugent, Bloodrock, Status Quo, Cactus, Grand Funk Railroad, Foghat, Scorpions, Judas Priest, James Gang, Accept, Saxon, Humble Pie, UFO/MSG, Blue Öyster Cult, Iron Maiden, Nazareth, Motörhead, Bachman Turner Overdrive, Bad Company (though on Swan Song, Led Zep's vanity label), Mott the Hoople, Slade ...
Zep's dominance as a musical influence is very much an American phenomenon. Whitesnake is a good example - their music was still un-zep'ish on their early to mid period albums (when they reigned Europe and Japan, but couldn't get arrested in the US). Come Coverdale's urge to crack the US market, come the first marked Zep influence with Slow 'n' Easy on Slide It In (after dissolution of the classic Whitesnake lineup) and of course Still of the Night on the US-conquering 1987 album. All credit must go to Peter Grant who kept Led Zep touring the US (and pretty much nowhere else) so incessantly until they had even a country as huge as the US in their pocket. He sure had a master plan, he criss-cross-vaccinated the biggest music market in the world with his protegés.