Interval training may be a little too tough a replacement for Hill training. Hill training gives you an extra strength because we get a little pace pressure and little tempo variation in, which can be used in races where one tries to hang on to others, or move up to the next runner, etc.
Hill training has to be understood as either trays or other form of extra resistance. It can be heavy terrain a la sand, high grass or you can press the tempo a little extra. The latter is the easiest. In each training zone Z1, Z2 etc is there an interval you can run within fx 6:09-5:30/km, as in your Z2. The press means that you then try to put you at 5:30. You can also run 5:30 in the long stretch and then 6:09 in the short stretch. It will be similar to backs up and down. Say your plan eg 9 min transadddot Z2, you can of course run 4 min 5:30 6:09 and 4 min, 1 min 5:30.
Alternatively, we need to completely change your plan, so it is free of hills. To what suits you best.