Zagora sits at the end of the Draa palmeraie, about a day’s drive from Marrakech if you accept a full road day. The dunes nearby are real sand, and a sunset there is still a sunset. They are not Erg Chebbi.
Merzouga’s Erg Chebbi dunes rise in a compact erg east of Rissani. That is the Sahara most people picture. Getting there from Marrakech wants three days; from Fes or Errachidia it can be two.
Choose Zagora if you only have two days from Marrakech and still want a camp. Choose Merzouga if the dunes are the reason you came. Mixing both on a short trip is wasted driving.
Read the 3-day Marrakech to Merzouga desert tour or the 2-day Zagora overnight and believe the hours. Then look at Morocco desert tours if you want the wider list.
Further reading from an official source: Visit Morocco guide to Errachidia, Midelt and Merzouga (Visit Morocco — Errachidia, Midelt and Merzouga).
