I typed that and hit submit as soon as I could! Ill be a bit more detailed ZZ are true succulents, semitropical succulents maybe, but they are not big fans of water, I root cutting is dry medium, watered rarely, the cutting often yellow up bad. Water in the presence if open wounds is bad, if its under the ground then u can count on numerous pathogens in there too! Bad news for and open wound on a plant that's not rapidly growing! I'm going to guess that it was the root prune that caused this, I've noticed damaged zz roots often(always?) die off when severely damaged, such as being whacked in half... They may lose all the old roots, wet or dry, but if kept moist, and the tuber is below soil, which it almost certainly is, then rot may progress into the tuber, as you've seen! Best case... You lose lots of leaflets. And several full fronds, the plants will never be the same, but given time can fully recover! The worst case is grim, ur clearly a good gardener, no need to discuss worst case! I have this same issue with zz, they just want to be left alone! I can't do that very well... Don't give up hope tho, get em dry, then clean em up good, as u have been, I'd let em sit a day, maybe 2 out of the soil... And then once satisfied I had stopped the rot, I would prop them up in dry medium, not so super dry as perlite straight outta the bag, that will desiccate them, but very dry mix, as if they r planted, but they really won't be! And at that point I'd let them sit for a good long while, no direct sun, no pouring water, occasionally mist, and occasionally lift them from the medium and check for more rot, then reprop them up in the pot of dry mix. This will keep their shape uptight and not twisted, and eventually u will start to see root progress, at the point I see even, ample root nubs distributed all around I'd then repot them in a more stable soil, basically, without roots the plants are cutting and need the same treatment... I'm so sorry, they were marvelous plants! It's awful killing off plants u love, but u can save them, and restore them to their former glory!

Both are Echeveria. Neither is monocarpic. The first looks similar to the hybrid 'Truffles'. Better pics would help ID.

If you goggle "yellowing of zz plant leaves", it will tell you to remove the plant from the pot and repot in fresh soil, removing all the rotten roots. Chances are that it has been overwatered. That "weird plant" that is growing in the pot is the zz flower. I have a zz plant growing in my garden and I rarely water it.

If this occurs (with ZZs) when you can still detect moisture deep in the pot with a "tell", you're very likely over-watering or one of the damping-off fungaluglies are at work rotting roots. If it doesn't regain turgidity and plump up within a day after-watering, serious damage to roots has likely occurred due to a prolonged period of dry soul and root desiccation. A high level of dissolved solids (salts) in the soil solution can also cause the symptoms shown. Using a 'tell' Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant. Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor. In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water. Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'. One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue. Al