i am in zhuhai now. I came to zhuhai by the bridge on March 6th. (FYI, they now have a fixed schedule now. when I came back, I was told once every hour. So if I didn't catch the current bus I would have to wait an hour.)
This was before the Beijing quaruntine law, but I did have some issues coming in. I travelled by US passport as I am not a HK citizen (no HRP). I had to wait almost 30 mins to be processed and there was no line. I think they were deciding whether or not i could even enter Zhuahi. I think the only reason they let me in was because my son was with me and he does have an HRP. The reason I had to wait so long was because i had to wait for an immigration official to get dressed up in full medical gear to process me. I also had to go through a different immigration line. The Customs officials cared more about where I was from than what was in my bag as they saw me using the special line.
As far as i can tell, the quaruntine law is just for Beijing as all the news only says Beijing. As the law changes every day, i cannot say if you will or will not be quaruntined in Zhuhai. I believe that it will be up to the Immigration official that you get and how they interpret the current laws.
Make sure to have a chinese translation for the address of wherever you are staying. Also contact information for someone in China (with a china number) as a secondary contact source.
I think it is ok for you to try. The worse case if you don't want to be quaruntined or they won't let you in is that you just go back to HK. I doubt they will force it on you as long as you didn't enter the country.
edit to add: I am not under quaruntine and did not have to be quaruntined.