I think the similarity to Zenith lies in the sixties Zenith timeline and the superhero group Cloud Nine, with Mandala et al. That was basically a psychadelic superhero group. As there have only been two superhero strips in 2000AD and both have featured some similar ideas, comparison is going to happen.
The story could very easily have been a Zenith 60's story with very little effort. With the psychadelic heroes opening doors to dimensions and letting bad things through and encountering a Charles Mansion style superhero.
That isn't to say anything has been stolen, borrowed or cadged, I don't believe it has, but the similarity is there.
My main problem with Storming Heaven is that there are no characters in it. You don't have any contact with it, it just sort of passes you by. I don't dislike it at all I'm just not very involved with it.
Well, there will always be people who like somthing and don't like somthing. I've noticed a lot of the strips seem to settle out at around 7 in the votes, either just above or below.