Pfft, you can farm that snake if you grind a little.
I've played FF7 a number of times and I'm still not totally clear as to what the fuck is going on. Did one of the imperfect cell implanted things wreck that snake? Astral project telekinesis a tree through it's fucking face?
I dunno man. I guess those were Sephiroth Clones walking around and one of them impaled the Zolom. The real Sephiroth was up in North Crater, controlling all the clones from there I guess.
I liked FF7's story a lot more the first time I played it, when I thought Cloud really was a former SOLDIER 1st Class and not just a mentally-ill cosplayer. And I also thought you were encountering the real Sephiroth throughout the game, not clones. I thought that one for years actually and I still kinda just pretend it's the real Sephiroth the whole time. Makes no difference to the plot and makes the character way more interesting.
As far as the Zolom goes, you can completely break FF7 at an early point using that fight. Grind outside Midgar until you're strong enough to survive a hit of Beta (over 2000 HP I think), put your characters in the back row and spam -ara spells or whatever, then when the Zolom is defeated and it does its Beta final attack, your character with E-Skill learns it. That attack is so ungodly powerful against mobs at that point in the game that you'll be able to one-shot pretty much all the random battles in Disc 1 as long as you have the MP to keep using it. The bosses will also be trivialized.
If you can get an Elemental materia before that (I think you can), pairing that with Fire materia on the E-Skill character will get you Beta at an even earlier level, without having to grind HP beforehand.
I think I did all of this a few years ago and have an FF7 file with a completely overpowered party right outside the Chocobo Ranch in case I want to play it again. I'll go check and see if I can get a picture of it.