Midfielder Dlamini - who was in demand following the team's relegation from the topflight last season - has signed a new three-year contract.
Zimbabwean goalkeeper Murambadoro has penned a four-year deal.
“I told myself that this a club I want to really play for when I came here, so it wasn’t too hard to recommit,” Murambadoro told Usuthu's website.
“I believe with guidance and with the experienced players we have, we can all help the younger players reach their potential and together put AmaZulu back to where we belong.”
Murambadoro linked up with the promotion hopefuls in the January transfer window.
Dlamini joined the Durban-based outfit in the 2010/11 campaign from African Wanderers.
Meanwhile, AmaZulu have parted ways with striker Darren Smith on "amicable grounds".