hum not sure i understand what you want to do...
Anyway, AFAIK MCDPatches are used to overwrite values of MCDs, so you can modify the stats of a MCD directly in the rueleset; for example: if a MCD has a armor 10, you can just add an MCDPatches entry that sets it to 50 and you're done.
To implement zrbite in UFOEU i guess you have to regularly make the zrbite-related MCDs (the TFTD engine), then link it to a zrbite item in the ruleset, using this method:
you can also link an MCD to an item, adding a specialType entry to the item; the MCD then should be given the same value to its Target_Type.
example:
specialType: 30 (in ruleset)
Target_Type 30 (in MCDEdit)
(Use a value of 20+ because some values -up to 14 iirc- are already used; max is 99 i think).
The linked item is automatically recovered if that MCD is still undamaged by the end of a mission (1 item for each MCD present on the battlescape).
Then i guess you can use the item to manufacture a craft..? i'm not sure about this.
If you want to check it in practice, i use this method in my mod for human craft missiles.
Or another method is to directly place, using ruleset, items in map: make a zrbite item (i guess you could make it invisible, AKA transparent floorob) and place it on the tile which holds the engine MCD.
Again i use this method in my mod, to spawn stuff like firearms on the empty shelves, or psiclones on altars.