Finished

Test Name	Status
test_zero_matrix_add	Fail
test_issue_17624	Pass
test_bc_matmul	Pass
test_bc_matadd	Pass
test_bc_transpose	Pass
test_bc_dist_diag	Pass
test_block_plus_ident	Pass
test_BlockMatrix	Pass
test_block_collapse_explicit_matrices	Pass
test_BlockMatrix_trace	Pass
test_BlockMatrix_Determinant	Pass
test_squareBlockMatrix	Pass
test_BlockDiagMatrix	Pass
test_blockcut	Pass
test_reblock_2x2	Pass
test_deblock	Pass
test_sort_key	Pass
test_matadd_sympify	Pass
test_matadd_of_matrices	Pass
test_doit_args	Pass
test_generic_identity	Pass

     def _blockmul(self, other):
         if (isinstance(other, BlockMatrix) and
                 self.colblocksizes == other.rowblocksizes):
+            return BlockMatrix(self.blocks*other.blocks)
+            result = self.blocks * other.blocks
+            # Convert scalar zeros to ZeroMatrix objects with correct dimensions
+            from sympy.matrices.immutable import ImmutableDenseMatrix
+            from sympy.core import S
+            new_result = [[None for _ in range(result.cols)] for _ in range(result.rows)]
+            for i in range(result.rows):
+                for j in range(result.cols):
+                    element = result[i, j]
+                    # Check if element is a scalar zero
+                    if element is S.Zero or (hasattr(element, 'is_zero') and element.is_zero and not hasattr(element, 'is_Matrix')):
+                        # Create ZeroMatrix with appropriate dimensions
+                        rows = self.rowblocksizes[i]
+                        cols = other.colblocksizes[j]
+                        new_result[i][j] = ZeroMatrix(rows, cols)
+                    else:
+                        new_result[i][j] = element
+            return BlockMatrix(new_result)
         return self * other

xas