Точно))
<h2>Доставка</h2>
<form action="">
<input type="radio" id="deliveri_1" name="deliveri" value="1">
<input type="radio" id="deliveri_2" name="deliveri" value="2">
<input type="radio" id="deliveri_3" name="deliveri" value="3"> <!-- Если выбрали этот то... -->
<input type="radio" id="deliveri_4" name="deliveri" value="4">
</form>
<h2>Оплата</h2>
<input type="radio" id="payment_1" value="1">
<input type="radio" id="payment_2" value="2"> <!-- ...то этот станет недоступен -->
<input type="radio" id="payment_3" value="3">
<input type="radio" id="payment_4" value="4">
<script>
var selected = document.querySelectorAll('input');
var makeDisable = document.getElementById('payment_2');
for(i=0; i<selected.length; i++){
selected[i].addEventListener('change', function(event){
event.target.id == 'deliveri_3' && event.target.checked?makeDisable.disabled=true:makeDisable.disabled=false
})
}
</script>