The zips only let the covers come off so far, there are sewn in metal rods just inside the bolster that are a pig to remove and refit. the base cover is also held on with hog rings and not really a diy job. Get a wet vac from b&q for £30, a numatic george fishtail off ebay for a couple of quid then remove the seats from the car, its only 4 bolts each side. Taking the seats out lets you deep clean all the nooks and crannies of the carpet. The whole interior comes out an x-trail in under half an hour. remember to disconnect the battery before unplugging the seat airbags.
To get to that stage you only need to undo 12 bolts, about 10-12 screws, release a load of easy to pop off trim clips and some easily accessible wiring connectors. Piece of cake with an li-ion impact driver. It's a dream to work on, I forgot how easy jap motors are to take apart and rebuild. Not one broken trim clip either unlike trying to do even a minor job on a bmw or merc, the only other japanese car I've owned was my first car, a Y reg datsun stanza. The only downer was the lack of sound deadening on the panels and sound insulation in the doorcards, I used a load of dynamat and felt on the floorpan, in the doors and tailgate and the car is much quieter on the road now, and the doors have a nicer feel when you close them.