Hey man! I played Goliath back in 2015 and i had an absolute blast with it, so i recently decided to play Corona Trials and Calamity Canyon, and i was not disappointed! Both maps are fantastic, Corona Trials is a great easy-to-play map for beginners with a nice difficulty curve and Calamity Canyon has a very good spin on the open world format, with an interesting setting and layout. Both aren't very long but they're great experiences and i'd recommend them to pretty much anyone looking to get into CTM maps.
The health system you're using is more interesting than the vanilla food system, at least for CTM maps. It makes the beginnings much faster and the fights are more fun, the fact that you can't rely on constant regeneration forces you to think about what you're actually doing, your stuff and how you use it.
I LOVED the aesthetics of both maps final zones, i won't spoil anything for those who want to play the maps, but i will simply say that those places scream "i'm the last place of this map and you're going to have a fun time here, enjoy the ride".
Let me say i 100% agree with you on the decision to replace vexes with zombies. On the last wools of Corona Trials, the vexes were not fun at all. Mojang needs to do a rebalancing of these mobs.
I've just two minor "complaints", just some stuff that you can improve if you want : don't hesitate to make custom mobs, even if they aren't too special. For example, in Corona Trials the mineral mobs, i liked them a lot. They're just skeletons with a custom appearance and different stats/enchants, but they're enough to provide a lot of welcomed variety. Sometimes, instead of putting just a vanilla zombie/skeleton spawner, giving them custom armor and head will make the place much more interesting.
In the same fashion, variety in loot goes a long way to make exploration more fun and exciting. Sometimes on the maps you get classic, vanilla tools or armor. It's fine, but what if, instead of putting say iron armor, you were to place more "unique" lower tiers of enchanted armor? For example i liked the duragold armor and tools, that was a nice idea. The more variety there is, the better the map becomes, in my opinion.
Anyway, i'm now going to play BigLeaf Forest and Myriad Caves, and i can't wait for Untold Stories VI! Thanks for producing some of my favorite CTM maps, keep going dude!
Oh and i hate self-promotion, but i also recorded my playthrough of both maps, like i did for Goliath back in the days. It's in french, and Calamity Canyon is currently ongoing, here is a list to the playlist if you're interested. Corona Trials will begin as soon as Calamity Canyon is over, in like three weeks or so.