I love the Z, but I wont pretend its a comparable product at all. These are totally different machines, with very different intended purpose and target audience. It really depends on what your goal in brewing is, if you want to brew your own creations you need something other than a Pico, whether you need a Z is up to you. Ill try to compare the two products since that was your question.
The Z is WAY more involved than the Pico. I can brew two Pico batches in less time with WAY less effort and hands on time than one Z batch, and two Pico batches is a little more beer than a standard Z batch. Cleaning the Pico is so much easier and quicker than the Z too. The post brew cleaning routine of rinses and dealing with the bulky step filter are the one pet peeve of mine with the Z. The first time you clean a 5 gallon keg you will appreciate the little Pico kegs you can clean in the sink. Again, these are to be expected with the bigger machine but you asked for direct comparison.
I am going to assume you are a new brewer and dont have most of the additional equipment needed, because there is additional stuff you will need to brew on the Z. You will need a scale for weighing grain, and a mill for crushing the grain. You will also need a jewelry scale for weighing small amounts of hops and adjuncts. You will want a hydrometer or refractometer, which are pretty pointless for the Pico. Depending on your water source, you may want to use distilled and need to add brewing salts and get a ph meter. Then theres fermentation chamber, and kegging equipment, and Im sure some other stuff Im forgetting. Point is that its not as simple as dropping a Pico pack in and pressing go, and the complete package of everything needed is not included like on the Pico.
Then there is storage, may not be an issue for you if you have a dedicated brewing space. I dont, I can easily store the Pico in kitchen cabinets and toss it on the counter when I want to brew. The Z is much bigger and heavier, I ended up buying a cart that I roll out from the hall closet to kitchen when I brew, my wife really wants that space back. Then the additional equipment needs a home and has to be brought out on brew day. You will also quickly have a grain silo and hop farm, as buying ingredients by the pound creates additional storage. Again this may not be an issue for you, but its got me in the middle of a brew shed build I will hopefully finish this decade. The equipment and storage will be there whether you move up to the Z or other brewing method, its just a really nice thing about the Pico not needing it.
I find it laughable to talk about price per batch, someone even thinking about dropping $2K for a 2.5 gallon wort maker probably doesnt care much. Besides, the Z is very inefficient, if cost per batch is a concern there is much cheaper equipment that will use less ingredients, even cheaper batches!