Learning COLL as a stepping stone isn't really a great idea from my experience. The only thing you gain from it is recognising the CP (Corner Permutation) but that can be learnt without COLL. Most of the COLL algs are just slower for 2H solving compared to the standard OLL alg, and COLL only really has use in OH where EPLL's are just so much better than regular PLL's.
Instead I would start out learning 2GLL (2 Gen Last Layer), where you only need RU moves to solve the cases. Unlike COLL this is more useful and will stay useful no matter how much ZBLL you use. Where as with COLL you will need to change from recognising only the corner patterns into the full edge pattern when learning the ZBLL's for each COLL case. 2GLL is about 2 times as many algs as COLL with 84, but they are also very easy to remember and execute since they are only RU moves, but there are some cases where the RU alg is just slower than say an RUF alg. Even the Sune and Anti-Sune 2GLL's are worth it to learn with how ergonomic they are, compared to COLL where the Sune and Anti-Sune cases are just not worth it.
docs.google.com
Then once you finish with 2GLL you can move on to learning a full OCLL set at a time, for example full T. It is best to learn a full CP set at a time, so 12 algs for one corner pattern. There are 6 different corner patterns per OCLL, 4 for H, so learning all 12 algs from one pattern is better than learning say 2 algs a day. This is because when you see that corner pattern in a solve instead of needing to spend extra time to see if it's one of 4 algs you learnt, you can just go straight into the alg because you know all 12 for that pattern. Make a copy of this spreadsheet to also track your ZBLL progress, and for some optimal algs with many different options for alg choice in both OH and 2H.
docs.google.com
I would also recommend learning BH (Baum Harris) recognition because that is another place where people lose a lot of time. With BH you are able to recognise every ZBLL from 2 sides, similar to 2 sided PLL but there is more to it. Learning BH is a bit difficult but if you stick with it then it will save you a ton of time and effort trying to relearn every case with BH recognition. You can use this sheet to learn BH or if you want to look at other recog methods and see if another one stands out to you, but I would stick with BH since it is so good once you learn it. Try to come up with your own names for each of the 12 BH patterns, something that will be meaningful and helpful to you. This way you should be able to recognise and associate the cases quicker and better than just using its visual look. You can make associations with whether 2 adjacent stickers are adjacent colours, opposite colours, or same colours. But make sure that you don't come up with something that can be applied to multiple cases because that will mess you up during solves. You can also just stick to using one recog angle, like for Sune being a U' away from standard, instead of trying to learn it for all 4 AUF angles. That is only really useful for top level cubers who want to be as quick as possible.
docs.google.com
Be sure to learn both the BH pattern and the AUF while learning the alg. Otherwise you will need to relearn them later on. Learning the AUF will also be very helpful so you aren't trying to predict what the AUF will be mid solve, or just trying to react to how you will need to AUF because that will cause you to mess up a lot of the time. The better you associate the BH recog and the AUF with each alg, the quicker you will be with ZBLL, so go slower than you might think you can so you can really build a strong connection between each alg, recog and AUF.
Be sure to review your algs A LOT because the number one reason most people don't do well with ZBLL is that they forget the algs. You can use trainers such as bestsiteever, not for the algs because some are outdated and there are better algs on ZBLL sheets, but for it's trainer which has been immensely helpful for my ZBLL practice. You can also make notes for each case, so if you need a bit of extra help when learning the alg, BH recog, or AUF you can make a note on that case, or you could also go through each alg and make a note about that so you can always have that to look back to.
A timer-like tool to learn and practice zbll algorithms. You can specify ZBLL cases & catigories to practice, recap forgotten ZBLLs, create presets to practise and learn. More info on the speedsolving thread
bestsiteever.ru
I know this is a ton of information so if you need any clarification just ask and I will try to help you out.
