I thought this was asking about the game item of maps and was wondering what a hardcore map was.
I have two hardcore worlds and I started both relatively recently. Both this year, the first one a little earlier in the year and the second one just the other day. Yes, I have two hardcore worlds concurrently, and I worry that might make me more careless in the newer one because I might feel like it's expendable. I feel relative safe in the older one by contrast, as I'm already established in that one, but I ultimately consider both "losses that have yet to happen".
The newer one especially I feel like I'll lose sooner rather than later though, and as my first hardcore failure. I'm playing under far more restrictions in that world than I already am in the first which only makes it all but certain. Not "ultra hardcore" (which disables heath regeneration), but no enchantments, no potions, no villager trading, no totems of undying, no farms, no elytra, no shulker boxes, and no F3 or other things (map programs, chunk base, etc.) that expose "information I shouldn't have". Without those restrictions it would feel too easy (even the other one has restrictions but not as much as the newer one). I've been playing survival for over a decade so even though I never tried hardcore until this year, I felt like vanilla hardcore with no restrictions would be less of a risk and have no purpose, so I put restrictions in place to give them purpose.
Baby zombies are something that used to panic me, but I'm very calm with them now. What helped me was to rationalize that despite looking like they are running, they equal the player walking speed, and to time the attack, maybe even after it hits you and stops moving momentarily because syncing issues occur due to how "fast" they move. Especially with a shield, it's easy. They appear scarier than they are.