For UHVs that are too hard, if you have others you know of aside from the Khazars. Let me know.
I haven't played (let alone achieve) all UHVs of the modmodmod, but i had troubles with Zulu's "kill 30 units" objective - the problem is that there might be less units in colonial forces. I had to give up my cities twice on the Congress and hunt Frigates with Galleases, and still was one unit short of UHV2 (however, the Dutch were very passive this game, so probably it's not a general case). Their UP (as well as UU and UB) is wildly fun tho.
Shu might be a bit too hard overall, but i can't say i was really tryharding it; i've tried to meet most UHV before Qin/Wei (a bit sad that there are no references to my personal favourite of the Three Kingdoms) spawn but it seems to be the wrong route (in which i was forced by Barbs conquering Xia early and forcing me to replace Zhou dynasty early), instead the idea is to consoldiate the South first, i presume?
Side note: Armenian UP is really bad: they have miniscule core, and their only city (Dvin) can be attacked from outside the core, making the UP useless both for and against human player). I'd suggest replacing it with something like +1

from hills in core because Dvin is impossible to grow before Machinery, which is ironically past Armenian peak of power, and current core population is barely enough to keep historical lands - this is a bigger problem that it appears; Armenian UHV requires a very long game (i think THE longest in turns), yet pathetic core means you better skip turns until 1919 and mass Statemen. I've abandoned my UHV run because trying to conquer even Asia Minor leads to collapse, and there is very little else to do.
Side note 2: around 400 AD, huge stacks of European barbarians (mostly melee units) migrate through Caucasus. It happened in both Parthian and Armenian games, around the same time. Possibly it's caused by Barbs trying to migrate to the Northern Africa (Egypt) with Constantinople forcing them to go around the Black Sea