What and where...
You are seeing existing zones of engines (from Zones.cfg) for Type 7c hull (stock game).
You can use existing zones or you can create new types of zones in Zones.cfg and use them.
Your actions:
* Zones.cfg. Create a new zones in the list... eg:
192 = MyDEngine1
193 = MyDEngine2
* Zones.cfg. Create two sections in UBoat Items part... eg:
[MyDEngine1]
...
Effect1 = ...
...
[MyDEngine2]
...
Effect1 = ...
...
with existing (in particles.dat) or new effects.
* Create new boxes in NSS_Uboat7 *.zon with new zones Indexes.
...
This is a simplified flow chart.
Sorry if I missed something.