Letrozole + HRT for ovulation induction

I am 40-year-old female trying to get pregnant. My estrogen levels and my AMH are rather low and my follicular phase very long of 27 days. Before going for IVF I am trying to improve my ovulation. My gynecologist gave me HRT (estrogen gel) that I should use every day. I should also take Letrozole 2,5 mg from cycle day 7 to 11.
My question is, can the estrogen gel interfere with the Letrozole (anti-estrogen) and reduce its effectiveness, since they have the opposite effect?
The second question is regarding the timing. Letrozole is normally taken on days 3 – 7, can taking it with a delay also reduce its effectiveness?