Is it worth doing the book grinding for Zenith weapon at Level 80 WAR?

[Hasrat]

Just know what you're getting into. The level 50 relic grind was a bit of a unique case, where devs were inclined to incorporate nearly every aspect of the game at the time into the process. After books, you will still need:

A supply of combat materia, grades 1-3. These can't be found from any vendors, and can run expensive on the MB because of it
Same step, will need to run many special level 50 treasure maps, either requiring Poetics, or a once-per-day quest (the item rewards can be bought with Allied Seals as well)
Grind for "light," which typically involves running the same low level dungeons a couple dozen times unsynced.
The penultimate step will cost 400,000 gil, 80,000 Company Seals, 800 Poetics, at a minimum. There is an additional step of purchasing and desynthesizing a set of items which can also get costly, all for materials to then craft specific level 50 items. If you don't have crafters leveled or otherwise can't be bothered, the finished products will be available on the MB, at an additional cost.
Plus one last step very similar to the "light" grinding, not quite as long, but still requiring a minimum of a dozen runs of whatever low level dungeon you're not sick of yet.

Personally, I wouldn't recommend trying to push through one weapon all at once. The whole thing is an incredibly tedious process, better to chip away at a little progress at a time, whenever you've got the energy, and step away before it completely drains you.

[Sworly]

Just know what you're getting into. The level 50 relic grind was a bit of a unique case, where devs were inclined to incorporate nearly every aspect of the game at the time into the process. After books, you will still need:

A supply of combat materia, grades 1-3. These can't be found from any vendors, and can run expensive on the MB because of it
Same step, will need to run many special level 50 treasure maps, either requiring Poetics, or a once-per-day quest (the item rewards can be bought with Allied Seals as well)
Grind for "light," which typically involves running the same low level dungeons a couple dozen times unsynced.
The penultimate step will cost 400,000 gil, 80,000 Company Seals, 800 Poetics, at a minimum. There is an additional step of purchasing and desynthesizing a set of items which can also get costly, all for materials to then craft specific level 50 items. If you don't have crafters leveled or otherwise can't be bothered, the finished products will be available on the MB, at an additional cost.
Plus one last step very similar to the "light" grinding, not quite as long, but still requiring a minimum of a dozen runs of whatever low level dungeon you're not sick of yet.

Personally, I wouldn't recommend trying to push through one weapon all at once. The whole thing is an incredibly tedious process, better to chip away at a little progress at a time, whenever you've got the energy, and step away before it completely drains you.

Good lord, that sounds like a nightmare ;n;

Yeah, I put it aside for now until I at least manage to finish up Stormblood first. Don't want to burn myself out on the least desirable aspects of the game

[Hasrat]

Being high level, you have the advantage of blitzing through most of your chosen dungeon hells in a matter of minutes solo unsynced, as long as you ignore all the treasure and paths and even all the trash mobs. Even still, repeating the dungeons enough will still eat up a couple/few solid hours of your time, and it is indeed mind numbingly tedious.

Every expansion has some manner of grindy quest for shiny weapons at each level cap, and yeah, they're all a bit of a chore to get through. But, for players at the time, there's often little else taking up their time once they've completed each expansion story.

As long as you've still got story to get through, that's usually the better focus. Some blue quests may still unlock new things that might be interesting to dip into. Tribal quests are easy daily sources of chunks of exp, good for jobs that aren't receiving all that juicy story quest exp. Optional dungeons/trials/raids can be a fun distraction. Among all manner of other non-combat options. But story quests are often considered "the good stuff" until/unless you're just looking for something different to do for a bit.