Off the top of my head, you want a means of tracking the last input (both axes) and how long ago it was, and how long it was held. So that initial input will start a couple of counters (delta to next input, input hold time) (maybe use delta time or a tick counter). Then on the next input, you’ll want to record both axes on input and then figure out a reasonable tolerance check for the next input, to ensure it’s pretty close to being in the same direction twice. Obviously you’ll want a means to check and reset those counters so you know when it’s appropriate to listen for a second input.
I’m not sure if you want to filter other input types (you may want to hold down the trigger to fire and sprint for example).