Hi - you need two flags. One for each sensor.
I'll use the simple method of going into a waiting loop after you detect an interrupt in either sensor.
During the waiting loop, see if the other sensor's flag changes to True (detects an interrupt). If it is True, then that counts as an event, and you know the motion of the object.
If there is no further change within the time limit, then reset both flags to False. Resume idle mode, waiting for the next sensor interrupt.
If you are not in a loop, and the other sensor's flag is False, then start a timer. The other sensor may go True within the time limit. If it does then count that as an event (per above).
If you wish, you can use one variable as a status flag, and set individual bits to zero or one.