The time period you've picked is highly interesting - the death of the capital Ship and the rise of the Aircraft carrier.
Assuming that the level of Gunnery is that of the 1940s - hell, let's pick an Iowa class battleship and it's mechanical computer for gunnery - your fighter planes launched from an aircraft carrier type airship are going to be much more effective.
So, let's talk about your airships - what speed are they travelling and what altitude are they reaching? WW2 era was at around 20-25,000 ft. Anti-Air guns (like the Flak 88) were capable of reaching up to those heights. Given their mass, I doubt they are going to be flying as fast as a WW2 era heavy bomber - so they are going to be more vulnerable to flak that way but more importantly...
Their size makes them much more susceptible to being hit
Now, you've said they have Armor - and given the upper-limit of length being 900ft, that's longer than an Iowa class Battleship - so let's assume an equivalent weight (we'll get to that) - between 50-60,000 tons. That's also assuming a similar all-or-nothing armor scheme. That's a lot of Mass. So again, they are going to be sloooooow
And before you say 'We'll just armor the bottom' - Flak can be set to airbust above the target.
In short - such large, slow vessels are going to get torn apart by AA batteries, even ones as innaccurate as the 1930s and 40s.
Being a mobile flying base for smaller Fighters and Bombers? That starts to make a whole lot more sense. You would keep them away from the Flak batteries, but close enough that your friendly aircraft can attack critical locations.
In terms of Gunnery, whilst the height advantage would mean significantly increased range - the Calibre of shells you are firing and the distance you would need to engage at to be safe from return fire would make it dubious at best:
Note, this talks about the 1980 refit, but We'll get to that
Total dispersion at 32 Km, 14/15 shells landed within 230 meters of the centre of the Target - pretty good shooting. But that's with Radar muzzle velocity sensors, modernized propellant and an updated FCS. I'm also not sure if the ship was sitting stationary or was steaming when the shots were fired.
Point is - with modern powder and advances in monitoring, we still have a pretty large dispersion pattern. I don't believe the relationship between range and accuracy is linear, so as the range increases, the dispersion increases at a greater rate (projectiles slow down, wind has more time to effect etc.) For WW2 era stuff - I think a dispersion at those sorts of ranges (again, safe from return fire) would be in the region of 500m - 1 Km.
You could make an argument that this is more accurate than a standard Heavy Bomber using gravity bombs, but the issue I have here is that those were predicated on carrying enough fuel and ordinance to get from point A to point B. Dive Bombers were far more accurate - but they were small and didn't have the range. By using Airship carriers, we negate this problem, we don't bother with heavy bombers, nor do we bother with big artillery - we just go with this.
That all said, Battleships are cool and were very much still considered the pinnical of Naval supremacy at the start of the War, so it's likely you'd have a lot of white-elephant ones armed with Big Guns, but once any form of serious combat happens, the advantages will soon show what is the superior weapons system