The only way to test the power diodes is to apply a rotating magnetic field to the stator coils and look at the resulting waveform at the battery terminals with an oscilloscope. Analyzing the rectified waveform will show the condition of the diodes. The bottom line is put it all back together and test it. The small diode is not a zener just a regular 1n4004 or something like that.
The power rectifiers are spot welded or plasma welded. They can be disconnected and re-soldered but, you better know what you are doing. Generally the problem is in the regulator or the brushes. Rarely but sometimes it is in the windings and power rectifier assembly.
The diodes can be had at any shop that rebuilds alternators. All the rebuilders do is: brushes, bearings, regulators & diodes.
Sounds like you dont have the right parts to the job and probably cant get them, so I would just cave in and buy the rebuilt one. Your first mission is to locate a source of parts. After that its easy.
I got too many cars!! Insurance eats me alive. Dave
78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k