<form name="zakaz">
Жилет меховой:&nbsp;<input name="isdel" type="text" size="4" value="3">&nbsp;шт.
<table>
	<tr>
		<td>
			Рукав левый 
				<div style="float: right;width: 20px;">
					<input name="detail" type="checkbox" checked value="1">
				</div>
		</td>
		<td>
			<select name="material">
				<option value="1">Кожа</option>
				<option value="2">Мех</option>
				<option value="3">Ткань</option>
			</select>
		</td>
	</tr>
	<tr>
		<td>
			Рукав правый
				<div style="float: right;width: 20px;">
					<input name="detail" type="checkbox" checked value="2">
				</div>
		</td>
		<td>
			<select name="material">
				<option value="1">Кожа</option>
				<option value="2">Мех</option>
				<option value="3">Ткань</option>
			</select>
		</td>
	</tr>
	<tr>
		<td>
			<b>Застежка молния</b>
				<div style="float: right;width: 20px;">
					<input name="detailmod" type="radio" checked value="4">
				</div>
				<div style="float: right;width: 20px;">
					<input name="detail" type="checkbox" checked value="3">
				</div>
				<table>
					<tr>
						<td>
							Пуговицы
							<div style="float: right;width: 20px;">
								<input name="detailmod" type="radio" checked value="5">
							</div>
						</td>
					</tr>
					<tr>
						<td>
							Кнопки
							<div style="float: right;width: 20px;">
								<input name="detailmod" type="radio" checked value="6">
							</div>
						</td>
					</tr>
				</table>
		</td>
		<td>
			<select name="material">
				<option value="1">Пластик</option>
				<option value="2">Металл</option>
				<option value="3">Дерево</option>
			</select>
		</td>
	</tr>
</table>
<br>
<center><input type="submit" value="Далее"></center>
</form>

if (!checkbox.checked) {
        checkbox.value = 0;
    }

var form = document.getElementsByName('zakaz')[0];

form.onsubmit = function (e) {
    var checkboxes = form.querySelectorAll('input[type="checkbox"]');
    for (var i = 0; i < checkboxes.length; i++) {
        if (!checkboxes[i].checked) {
        checkboxes[i].value = '0';
        }
    }
};

<script type="text/javascript">
var form = document.getElementsByName('zakaz')[0];

form.onsubmit = function (e) {
    var checkboxes = form.querySelectorAll('input[type="checkbox"]');
    for (var i = 0; i < checkboxes.length; i++) {
        if (!checkboxes[i].checked) {
        checkboxes[i].value = '0';
        }
    }
};
</script>

var details = zakaz.detail;
for (var i = 0; i < details.length; i++) {
    details[i].addEventListener('change', function () {
        var td = closest(this, function (el) {
            return el.tagName.toLowerCase() == 'td';
        });
        var material = td.nextElementSibling.querySelector('[name=material]');
        material.disabled = !this.checked;
    }, false);
}

function closest(el, fn) {
    while (el) {
        if (fn(el)) return el;
        el = el.parentNode;
    }
}