My review of the ZeroLemon is live on Amazon:
https://www.amazon.com/review/R3A63...ag=hawk-future-20&ascsubtag=UUacUvbUpU5664785
Summary: battery life is exceptional, but the case is not for everyone. It is as uncomfortable as it looks. The bulk doesn't bother me as much as the shape of the case does.
The question you need to ask yourself is whether or not two day battery life is worth the discomfort. It's not terrible, but it is noticeable. For me, it's worth it just not being anxious anytime my battery drops before 50%.
It's less bulky than carrying a power bank and it's less of a hassle than quick charge or swapping batteries. If you're okay with having to always plug in or swap batteries, then don't worry about this and carry on. If you don't like having to plug in or swap out, then consider an extended battery (notice I didn't specifically say the ZeroLemon battery).
Unless you absolutely need 10000 mAh or you unless you absolutely hate having to ever charge or swap your battery, then I'd actually recommend a 6000 mAh extended battery instead. The ZeroLemon is great for what it is, but 10000 mAh is excessive and probably unnecessary.
If you want the most power possible, though, and don't mind that it's a bit uncomfortable to hold, then, by all means, get the ZeroLemon.