Step 1 :Given the matrix \[\left[\begin{array}{cc:c} 2 & 16 & -4 \\ 6 & 52 & -12 \end{array}\right]\], we first multiply the first row by 2 to get \[\left[\begin{array}{cc:c} 1 & 8 & -2 \\ 6 & 52 & -12 \end{array}\right]\].
Step 2 :Next, we add the first row to the second row to get \[\left[\begin{array}{cc:c} 1 & 8 & -2 \\ 0 & 4 & 0 \end{array}\right]\].
Step 3 :We then divide the second row by 4 to get \[\left[\begin{array}{cc:c} 1 & 8 & -2 \\ 0 & 1 & 0 \end{array}\right]\].
Step 4 :Finally, we subtract 8 times the second row from the first row to get \[\left[\begin{array}{ll:l} 1 & 0 & \square \\ 0 & 1 & \square \end{array}\right]\].
Step 5 :The missing entries in the resulting matrix are \(\boxed{-2}\) and \(\boxed{0}\).