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_blocks = self.blocks*other.blocks
+            # Convert scalar Zero objects back to ZeroMatrix objects
+            from sympy import S
+            def convert_to_matrix(block, row_idx, col_idx):
+                if block == S.Zero:
+                    # Determine the correct dimensions for the ZeroMatrix
+                    # based on the block structure
+                    rows = self.rowblocksizes[row_idx]
+                    cols = other.colblocksizes[col_idx]
+                    return ZeroMatrix(rows, cols)
+                return block
+            # Apply conversion to all blocks
+            converted_blocks = Matrix(result_blocks.rows, result_blocks.cols,
+                lambda i, j: convert_to_matrix(result_blocks[i, j], i, j))
+            return BlockMatrix(converted_blocks)
         return self * other

fortitude