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)
+            from sympy.matrices.immutable import ImmutableDenseMatrix
+            # Perform block multiplication
+            result_blocks = self.blocks * other.blocks
+            # Convert Zero objects back to ZeroMatrix with appropriate dimensions
+            def convert_to_matrix(block, row_idx, col_idx):
+                from sympy import S
+                if block is S.Zero:
+                    # Get dimensions from the corresponding blocks
+                    # For multiplication, the result block at (i,j) has dimensions:
+                    # rows: self.blocks[i, 0].rows (same as row i of self)
+                    # cols: other.blocks[0, j].cols (same as column j of other)
+                    rows = self.blocks[row_idx, 0].rows
+                    cols = other.blocks[0, col_idx].cols
+                    return ZeroMatrix(rows, cols)
+                return block
+            # Apply conversion to all blocks
+            converted_blocks = ImmutableDenseMatrix([
+                [convert_to_matrix(result_blocks[i, j], i, j)
+                 for j in range(result_blocks.cols)]
+                for i in range(result_blocks.rows)
+            ])
+            return BlockMatrix(converted_blocks)
         return self * other

Alone