Wow, that's not a lot of information, but I guess it counts as proof? I looked on Wikipedia and although there seems to be no information on the Led Zeppelin cartoon, when looking up the Grape Ape show that supposedly aired before the Led Zeppelin cartoon, I found that the Grape Ape Show was part of a block called The Tom and Jerry/Grape Ape Show,which began airing in September 1975, before it was extended to The Tom and Jerry/Grape Ape/Mumbly Showin September 1976. Like I said earlier, I'd heard that Mumbly was supposedly the show that replaced the Led Zeppelin cartoon. It is possible that the Led Zeppelin cartoon aired in the timeslot after Tom and Jerry/Grape Ape before the block was extended to include Mumbly, thus taking up LZ's timeslot.
