I don't have a Zenith so can't comment on it really...
I will recommend JLC if you are looking for accuracy

Panerai is good looking watch but depend how much you like big watch

IWC, classic and my favorite is Port and Pilot classic.
I do have some bad experience with JLC before my last acquisition, JLC Grande Reverso GMT.
First, i owned a 889/2. I bought it used. It's a master control series and i can't remember the model. I sent back richemont for service but come back still not up to my expectation and the watchmaker told me 889/2 is running within "that" (it was gaining > +10 to +20, can't remember exactly) range. Later i found out the 889/2 should be within COSC standard and it's 1000 hours tested. Wasn't happy and sold few weeks later.
Then, i bought a PAM190. It uses JLC 8 days movement as you all aware. Wasn't happy with the movement too because it's not really accurate either. Managed to sell it with some good price, so, no complain
Last month, i bought a new JLC Grande Reverso GMT, love it

I just done a week (actually 2 weeks, but the first week wasn't too sure because i didn't sync the time properly) of testing on its accuracy, after 8 days, it's +5 only and it is still ticking now.. I would expect around 9 days++ PR. But then again, the accuracy really depend on an individual, how you wear it and how you place it, etc.
As compare to IWC 7 days. The Grande GMT accuracy is far more better. Both my Port 7 and BP gain +5 to +6 daily.
PAM233 loses 1 sec daily as per my last check (i think last year :p).
In my opinion, for long power reserve, manual winding are far more accurate then automatic. I can be wrong but that's my opinion based on all my long PR watches i have.
OK, that's the movement part. Personally, I like only the classic look JLC. For example, the Master Control (dressy type), the MEMOVOX and the Reverso (I like only the Grande reverso because the size and thickness are just right), Duometre

The others i find too "extreme" but technically they are good watches, I will like to have it if i can start print my own money
Like Pete pointed out, JLC produces a lot of quality movement and. the same movement will not used in more then 1/2 model. I am surprise that JLC uses different movement in their AMOX Alarm and MEMOVOX Alarm since both are having same function (3 hands, date at 3 o'clock, alarm crown at 2 o'clock, etc). From this, you can see the effort JLC is putting in.
I will say, go for JLC if you looking for a good quality and value for $ watch (if you do some homework checking out the price on JLC, IWC and Panerai you know what i mean

)

good luck!
scott