Ok, that sounds feasible, but to make that a relevant test, YYYY.esp must place a new static or other object into the world, not just move a vanilla placement -- i.e., so the REFR has a local FormID rather than a vanilla Oblivion.esm FormID (00).
Then ZZZZ.esp must try to move that object.
I made a YYYY.esp that:
1; Created a new container and placed it in the world (renamed a barrel)
2; Placed a vanilla chest in the world
Loaded XXXX.esm and YYYY.esp (not active)
Moved the 2 objects mentioned above
Saved as ZZZZ.esp (no crash)
In game:
a. The barrel (1) remained where YYYY placed it. ZZZZ movement was ignored (makes sense)
b. The vanilla chest (2) was duplicated: one where originally placed by YYYY. Another where ZZZZ moved it to (funny, but kind of makes-sense-after-the-fact)
Same results with similar actions in Oblivion.esm
Rename an enchant, such as EnWeapFireDamage10Flame, creating a new one, then make a new sword (rename and create new) and assign your new enchant to the sword (on the weapon dialog).
Created an enchanted longsword ELS1, as you said, in YYYY.esp and placed one in the world
Loaded YYYY.esp, created a new longsword by renaming ELS1 to ELS2, placed one in the world and saved the ESP as WWWW
In game, both were there, but ELS2 didn't have the enchanted symbol in the inventory.