...... to avoid some backtracking and visit El-Jadida and Essaouira from Marrakech.... from Marrakech travel first to El-Jadida, from there travelling south to Essaouira...
https://www.lagare.ma/en/trajet-eljadida-essaouira_aller_2019-01-16.html
https://www.lagare.ma/en/trajet-essaouira-taroudant_aller_2019-12-16.html however you can travel to Taroudannt via Agadir and/or Inezgane (a suburb south of Agadir City)... and easily find another bus, or better and faster a public shared grand taxi from Batoire near Place Slam in Agadir, Buses travelling to Inezgane terminate beside the Taxi Lot...
https://www.youtube.com/watch?v=AbkmDP2vROI .... see bus station(Gare Routiere) in background.
https://www.youtube.com/watch?v=772uOKMHUUs
http://reversehomesickness.com/africa/taxi-fares-morocco/
further reading.....
https://www.lonelyplanet.com/thorntree/forums/africa/morocco/taghazout-to-ouirigaine#post_23219540 and....
https://www.lonelyplanet.com/thorntree/forums/africa/morocco/buses-in-essouria-area#post_23019605
If travelling onwards to Ouarzazate, do it from Taroudannt via Oulad Berhil and Talouine.... Talouine is an interesting little village to see in two parts either side of a river, a Bridge and/or a Ford for a stepping-stone exercise depending which end of the village you cross, the centre for Saffron in Morocco, with a Saffron cultural centre on the newer built by-pass main street/road, if passing worth finding and visiting, the displays are easy to follow and helpful staff, the best quality Saffron is available to buy.
On Taroudannt.... my favourite place in Morocco since 1992.... this is essentially an agricultural town with services in engineering, marketing and administration for the huge Sous Valley area and the southern slopes of the high Atlas mountains, it's the centre for farmers and their families to socialise, visit the hospital, secondary school and in recent times the University of Agadir has built a college for some popular courses to lead-on to students finishing at a more advanced level in Agadir latter.
It's a fun town, busy and lively with students from the wider area boarding here with relatives, or boarding houses. see following link for an insight....
https://www.lonelyplanet.com/thorntree/forums/africa/morocco/easter-and-itinerary?page=1#post_22435986
Have you formed the bones of an itinerary yet.? To mention, a copy of the Lonelyplanet Moroccan Guide is probably the best investment you can make, these pages won't be as good or complete, have a copy to hand as you travel.