Advice on crossing Morocco needed.

I am planning to travel from Madrid to Senegal, beginning in mid-January. I need some advice on the best route to cross Morocco from Tanger to Guerguerat. My main concerns are the safety of major national roads, the condition of secondary roads (especially after the floods in November in the South of the country) and my need to find the easiest and fastest route, as I need to save time and energy to cross the Sahara desert before it gets too hot.
Thanks in advance for sharing your knowledge on the roads of this beautiful country.