You can try to change the weight of the module in the systems table but doesn't always work and can cause other issues. I would use the hook_modules_implement_alter
function. You will need to unset yours and then add yours to the top or before the other module. Here is an example I used doing a hook_user_delete
and hook_user_insert
function users_module_implements_alter(&$implementations, $hook)
{
if($hook == "user_insert" || $hook == "user_delete")
{
unset($implementations['user']);
$user = array('users' => false);
$implementations = $user + $implementations;
}
}
Yours would be like this:
function users_module_implements_alter(&$implementations, $hook)
{
if($hook == "menu_alter")
{
unset($implementations['mymodule']);
$mymodule = array('mymodule' => false);
$implementations = $mymodule + $implementations; // Also could use array_merge
}
}