while loop grammar question

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

      I probably know the answer to this somewhere in the back of my
      head but right now it eludes me:
      
      #!/usr/bin/zsh
      
      for ((aa=1; aa < 10; aa++))
      {
          echo $aa
      }
      
      for ((aa=1; aa < 10; aa++)); do
      {
          echo $aa
      }
      done
      
      aa=1
      while (( aa < 10 )); do
      {
          echo $aa
          let aa++
      }
      done
      
      # return
      
      aa=1
      # This escape test isn't captured:
      while (( aa < 10 ))
      {
          echo $aa
          let aa++
      }    
      
       
      ... the for loop is fine with or without the 'do/done'
      construction but the while loop requires it -- it runs on forever
      otherwise.  The echo and the increment are looped over but it
      won't break.  I must know this, but right now it has me scratching
      my head.