I'm not sure A4000RAMTest would do much for me given the machine does not detect the ZIP modules at the moment.
The way that the fast memory addition works is that the system performs a check starting at 0x08000000 and then decrements every 1MB and tests again until it eventually sees a failure. Any 1MB blocks of memory it sees as valid in this continuous range is added as system memory.
If you have any kind of error (e.g. even a single data bit) at the first test, then it'll silently fail, and you'll have no system memory added for no obvious reason.
The purpose of A4000RAMTest is to report the result of each 1MB memory test so you know what kind of problem you're facing. For example, if you have a single bit error in the bottom 4 bits of the 32-bit word that was read back, but the upper 28 bits are OK, then you can conclude that the problem is with the first ZIP that has data bus D0-D3 connected. So this is exactly how it could help you.
But great that Chris has sorted out the issue you were having, he's done an impressive job with ZIPtest.