much better than Zardoz

It's a great space western

Not hard to do. Zardoz was an ambitious and beautiful but ungainly mess.

All I remember of Zardoz is the big giant head that spewed guns, and the nut sack that Connery ran around in. It's such an outlier in his resume.

Agreed.

Zardoz is an excellent film. The ideas of artificial intelligence and human immortality are well considered. Even the "telepathy" in the film makes sense if you see that it is actually mediated by the A.I.. Sure, it gets a little too arty and people find the costumes ridiculous, but human fashion has run a pretty wide swathe of weirdness over time and across cultures. My single biggest gripe with the film is its basic conservatism. Immortality is seen as unnatural and the community of the Eternals is depicted as a grotesque failure that needs to be destroyed. Like many of the "stagnant" civilizations that Jim Kirk wrecked in Star Trek, the world of the Vortex is a bit of a strawman; too fatally flawed and designed mainly to show us the flaws.
But the whole is beautiful, stunningly designed and overflowing with good ideas.

Yes.

The problem is that this film lacks any floating stone heads that belch guns out to worshippers, or Charlotte Rampling's entrancing eyes. If it had those things, it'd easily pull ahead in the rankings.