Hi,
Cats can carry objects but I wouldn't have the bag weigh more than a couple pounds (or roughly .5 kg.) She can open the ziplock, but closing it would be very difficult... I think instead of successfully closing it she'd be more likely to accidentally damage it / get it stuck and have to resort to folding it.
Plastic bags are also very fragile and cats are prone to damaging them with their teeth. This wouldn't be an immediate issue, but overtime would cause the food to go stale / depending on the hole size the food would fall out. @
Rowan: