We (Wade - MkIV4280, or something like that) took my ZF apart on two occasions.
First, we replaced the bolts on the ring gear, and safety wired them. That was accomplished in about 2 sessions of 5-6 hours on two consecutive days.
Second, we swapped out my second gear synchro, and swapped out my 5th gear for a taller gear.
The second project took a lot longer.
It took us about 2 or 3 six (6) hour sessions to carefully disassemble the box. My transaxle was disassembled for about 3-4 more weeks waiting for parts (you can read about my progress in my build thread).
Careful reassembly probably took us about two additional 6 hour sessions.
Remember, I’m a bonehead, and I’ve only done this exactly two times. But I will say that with the guidance of a guy who had disassembled VW transaxles, and being very careful, we were completely successful in both the synchro replacement, and the install of the taller 5th gear.
Guys who have all the parts, and lots of experience (Ron McCall, Lloyd, Roy , and Les Gray) may chortle at my pace - but it is what it was…. AND we got it done!
I will also say that Lloyd Butfoy was very helpful with some phone consultation, it seemed to me he had his hands full with his ongoing workload, but was happy to provide advice to someone working their own box…
A ZF is not magic, it’s just precision. It can be done if you can build a couple fixtures, and are (very) careful. BUT - It is complex!
Rocky