Help with friend who has high ping on our server

I run a server for me and 3 friends. Three of us live in the same country and have no issues playing the game as normal but one is in a different country and has 200+ ping.

He uses exit lag to lower it, otherwise its 350+ ping but there's a lot of problems for him while playing.

The most recent (after starting a fresh map) has been zombies disappearing for him while hordes spawn around the rest of us. Funny thing is that it runs smooth until he gets into a car.

We have car mods and others, but this is a new issue with this save. There were others on the previous one.

Is there anything we could do in the settings or could the mods or exit lag be the cause of the problems?

Running the server on my laptop with 16gb of Ram (5gb dedicated), decent Ryzen processor (cant remember the model) and 4070 ti. Internet shouldn't be the issue at 100gb down and up. Not sure what else you might need, but i can provide the specs as necessary

Thanks in advance