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)
+            # Multiply the blocks
+            result_blocks = self.blocks * other.blocks
+            # Convert scalar Zero objects back to ZeroMatrix objects
+            from sympy.core.numbers import Zero
+            from sympy.matrices.immutable import ImmutableDenseMatrix
+            # Get the expected dimensions for each block
+            new_rows = []
+            for i in range(result_blocks.rows):
+                new_cols = []
+                for j in range(result_blocks.cols):
+                    block = result_blocks[i, j]
+                    # If it's a scalar Zero, convert it to ZeroMatrix with appropriate dimensions
+                    if isinstance(block, Zero):
+                        # Get the dimensions from the original block structure
+                        rows = self.rowblocksizes[i]
+                        cols = other.colblocksizes[j]
+                        new_cols.append(ZeroMatrix(rows, cols))
+                    else:
+                        new_cols.append(block)
+                new_rows.append(new_cols)
+            # Create a new matrix with the corrected blocks
+            corrected_blocks = ImmutableDenseMatrix(new_rows)
+            return BlockMatrix(corrected_blocks)
         return self * other

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