Terms for subject Proverb containing could be

English	Russian
if the young man would and the old man could, there would be nothing undone	если бы молодость умела, а старость могла
if the young man would and the old man could, there would be nothing undone	если бы молодость знала, если бы старость могла
if the young man would and the old man could, there would be nothing undone	если бы молодость умела, если бы старость могла
if the young man would and the old man could, there would be nothing undone	если бы молодость знала, а старость могла