Give it a try, worst case you need to change it back.

It won't affect your connection to Zen although it could prevent firmware updates later down the line - not necessarily a bad thing to keep those within your control either.

I have a 7530 AX with Zen and using A+A voip and not seeing any issues.

TR369 is also enabled.

I've been using A&A voip with Zen without any problems for nearly 2 years
The instructions I used to set it up are here

https://forums.thinkbroadband.com/voip/t/4749882-re-...

https://forums.thinkbroadband.com/voip/t/4779535-re-...

Unfortunately that hasn't worked, under the provider services tab there are the following checkboxes:-

Allow automatic configuration by the internet provider:- greyed out and checked, I cannot change this
Permit automatic updates:- unchecked
Observe the URL of the Auto Configuration Server over DHCP and PPP:- unchecked
Permit connection to your internet provider over USP (TR-369):- unchecked

Looks like a factory reset will be in order.

No need for a factory reset. Go into Internet/Account Info then in the top drop down box where it says Zen Internet click on the drop down and choose "Other Provider". Then configure your Zen account settings from there.

I tried both and it still is broken. Even after a factory reset I have the option "Allow automatic configuration by the internet provider
This setting allows the internet provider the secure (encrypted) transfer of the internet account information and login data for internet telephony on this FRITZ!Box. Not every internet provider or internet telephony provider supports this function."

Checked and greyed out so I cannot disable it.

A facrory reset will simply return the router to the state it was delivered in from Zen i.e with the Zen settings applied. The only way to get rid of them is as I said in my previous post - Go into Internet - Account Information and then change the preconfigured "Zen Internet" setting to "Other Internet Service Providor". Give it any name you like then complete the configuration options including your Zen username and password as shown in the welcome pack you would have received. Click "Apply" then when the router completes its configuration you will find that the "Provider Services" tab has completely disappeared.

I tried that earlier but it made no difference.

In the end it's Zen who have flicked a switch at their end via support chat to stop pushing changes to the router and it's now working. It might have been possible to somehow flash the standard firmware from Fritz!box on it I guess but I stopped looking once Zen resolved it. I had to go through support twice though as the first person claimed to have done something which didn't work. It also removes them pushing firmware updates but I can do that manually myself anyway.