My suggestions:
Increasing the timer before zombie invasion from 2 to 4 minutes. this gives players more time to plan out a spot to cade, and bring props. instead of it beeing as rushed as it is now.

Lowering the timer at the end of a round from 2 minutes to 30 seconds. we really dont need that much time at the end of a game. it gets to be tideous.

Increasing the timer between waves from 1:30 to 2 minutes.
Replacing broken props with new props is very time consuming even for the experienced cader. and 1 minute 30 seconds isnt enough.

For me the 2 mins before zombies is fine, mainly because I don't bother cading and let others do it lol.

As for the end round timer, I agree it ends up being people just sitting around for a minute and a half with nothing to do.

The time between rounds for me is fine, especially if the zombies are silly and just charge to their death giving you more time to fix your cade.

I cant really say much about the first two because I don't barricade anything, I just protect for when zombies come but, the end timer really should be shortened.

+Support for the end timer

Insomniac can you please make one big thread full of all the problems instead of creating a thread for every problem it would save people time.

+ Support. I've just recently started playing ZS and find this to be a problem when cading, especially when there are tons of people on. By the time I get the props into the room, I have about 10 seconds to make a cade. Then, I have a ton of people yelling at me to cade it, a ton of people throwing props everywhere, and a bunch of people jumping on stuff and standing in the way. While this is happening, I'm sitting in my chair crying and pulling my hair out.