My schematics are on my other computer that is giving me trouble right now and I was unable to retrieve it. There is a schematic on the ZB website though. As mentioned earlier, the base of the spool (the skirt with all the holes around the diameter) unscrews from the rest of the spool. That's where you'll find the main drag. The thing is, unless the drag washer was burned, this area generally sees no sand or water.
What a lot of people don't realize is that there's a secondary drag on the top of the spool. This is where you'll find seals get compromised and debris gets in that area. So that and the springs in the spool cap are usually the areas of concern and need servicing.
And when you take these areas apart, be very careful to not loose the small springs and clicker detents. They're a little tricky to re-install too. It just takes patience, it's not difficult.
This is generally what I've found on all the reels I've serviced for folks.
Here's the schematic link;
https://www.shopzeebaas.com/ProductD...ctCode=41003-A
Threaded Mode