heaven_ropes (im new)

This needs an overhaul.
The white and gray are overbearing. The flat ceiling and excessive fog insult my eyes. The fog really takes away from the clouds, which could look cooler with a better backdrop. You should try experimenting with skyboxes to make the clouds stand out while still making the map look like it's in the sky.
You mentioned the floor and ceiling are flipped but that isn't apparent from the point of view of the player until they go to map build and fly below the spawn area. You could make a landscape surrounding the playable area and a pool of water to reflect the build, much like ritz. Otherwise the premise is lost on players who don't have /spectate.
As far as the layout of the spawn area goes I think it's too restricted. You've made it exceedingly difficult to navigate the platforms without ropes while making them difficult to access, especially if zombies are involved. As a rule of thumb: it's a bad idea to climb ropes if a zombie is nearby unless you can juke them, and even then it's super risky. This risk is increased when the paths to the ropes are too narrow to facilitate the movement required. Truthfully some of the paths are just wide enough but you're pushin' your luck. That's not even mentioning that there aren't enough alternative platforms or paths on the way up, making climbing super committal. As it currently is you either climb the ropes or you don't. Either the map needs a more linear path to the top as a parkour map or you could commit to the idea of upsidedown architecture without relying on the ropes so much as a prorun map. Personally I think you should forgo the prorun area at the top and focus on making a visually appealing prorun area below the giant ceiling.
Nitpick: It's too difficult to read the font with the white backdrop but this is something you could fix with a more visually appealing skybox and less fog. I shouldn't have to look up every time I wanna read chat.

Hey toeu, thanks for taking the time to write a submission! Although this map does need some work like bandsag said (be sure to make those changes!), this is pretty promising. The spawn of the map makes it look like a one-route map, perhaps change that? Since ZS allows 30 seconds for people to spread before a person is infected, you may need to revamp the spawn area of the map to enable no mass to infections. When I looked at the map and timed myself, it took 30 seconds just to get to the 3rd platform.

The rest of the map does feature a few options and routes for which zombies and humans can play on; but the spawn... not so much. I am also concerned about the neo at (72, 96, 59). This could serve as a false route which many players may fall. To solve this, I would recommend removing a few blocks to allow a person to go through. If you do not wish to do this, adding a block on the side will do.

At (54, 92, 46), there actually isn't a way to get to the other sections, as the staircase is blocked off, and the ropes do not appear to lead anywhere. Try adding a few blocks.

The section on the top does seem a bit too 'extreme' and does not suit the map's duration (4m). As bandsag said, focusing on the bottom section might be your best bet. If you still want to incorporate this into the map, try making the bottom section a bit smaller.

There also are no killer blocks at the bottom of the map. Please add some killer blocks, and make the fall height less time-consuming. Humans can easily avoid zombies by 1. Waiting for a zombie to come, 2. Jumping into the void, and 3. Repeat. I like the spawn height though, as a keen zombie can stay at spawn, camping the respawn zone. It isn't detrimental to the gameplay by keeping the spawn height there, as falling into the void seems to be not probable and easy to avoid.

Overall, this map needs a bit of work, although I like some aspects such as simplicity and the environment. Keep at it, and the map will be ready for ZS!