I'm, thinking of using it for FMC.
If you want to use it for FMC, you're pretty much going to have to learn the move-optimal algs, and also heavily prioritise the shorter cases (≤11 moves).
I've got a few official sub-30 singles with ZBLL, but it's really not something you can rely on. Furthermore, if you're learning algs solely for using in FMC, you have to keep these in mind:
1. Optimal last layer algs that are 10+ moves long often don't have any "easy" structure (as in, they aren't just combinations of triggers), so you just have to memorise them by brute force.
2. Even if you know full optimal 1LLL, you should only expect to use 1LLL in solves maybe 20-40% of the time. It's often better to do 3c/4c/5c skeletons and insertions instead.
3. Given the above, if you don't refresh frequently, you may find yourself forgetting these algs.
4. This is going to be of almost zero use if you ever intend to switch to domino reduction, widely considered to be a vastly superior method for FMC.
edit: I don't mean to be discouraging! You just need to have realistic expectations on how much learning so-and-so method will help you with so-and-so event. In this case, learning ZBLL solely for FMC is just not that useful, and if you intend to take FMC seriously, perhaps learning DR is a better use of your time. But ZBLL is also useful for speedsolves—and indeed, much more useful for speedsolves than for FMC. If you want to try out the weekly comp's speed FMC event, where solutions are graded on both move count and time, it's also very useful there (roughly 60% of my solves use ZBLL).