Unfortunately, you are not able to split up a payment among different credit cards. Only one card can be used on one transaction.
...if it helps, however, you can add multiple credit cards to your subscription and go back and forth between labeling which credit card is the "default" card for the subscription. The "default" card is the card that will regularly be charged. In this way, you can get charges on different credit cards, rather than having charges accumulate on one card specifically!