So...
Ebonheart pact (110 hours-ish):
1.5 hours or so for Bleakrock and another 1.5 hours for Bal Foyen starter areas. Pickup the mage guild, fighter guild, and Undaunted guild membership in Davon's Watch along the way, and of course also start on the game main quest (Davon's Watch). Also enter Cyrodiil as soon as you get to L10, or do at least one Battleground random daily to unlock the Alliance War skill lines (and Rapids). Visit a stablemaster daily once you get your free mount, and train for speed first, then bag space.
Then 10-20 hours each for the next five zones (Stonefalls to The Rift), assuming you focus on each zone main quest but also explore to find wayshrines, do each delve, and find any overland skyshards. Try to do one random dungeon each day from L10 onwards (about 30-45 minutes), but otherwise ignore the mage guild, fighter guild, and undaunted quests and dailies. Ignore any prologue quests and also ignore the public dungeons until you reach cp160 and have some decent gear.

Coldharbour: (15-20 hours-ish) - then complete the main game quests.

You should also have reached L50 by this point, so also go to the Undaunted enclave outside Mournhold, Wayrest, or Elden Root, and pickup and complete the NON-DLC daily undaunted pledges in NORMAL from Maj and Glirion every day, to complete each group dungeon at least once for the quest skill points. (About 20 hours). This is also a good time to start researching the divines trait in every crafting item, or sharp/precise/infused trait on weapons, so that you can transmute traits on good items later on.

Cadwell's Silver: another 110 hours-ish going through the Daggerfall Covenant areas from Stros M'Kai, Betnikh, Glenumbra and through to Bangkorai. By this point you should have reached cp160 and should start trying to get some good starter armor sets (e.g. crafted, possibly by a guildmate or friend), upgraded to purple or gold for weapons. Start running pledge dungeons in Vet mode if possible, to get a monster helm and to get more progress towards your Undaunted skill line.

Cadwell's Gold: another 110 hours-ish going through the Aldmeri areas, from Khenarthi's Roost, Auridon, through to Reaper's March. At this stage, also try do each DLC dungeon pledge in normal at least once, for the skill points, and stop doing the other pledges unless you need the helm or it's an event.

Next stop - either Cyrodiil and start doing some PvP - but also try to complete all the town daily quests and get all the skyshards - or Craglorn. Both are fairly big and may require you to group up with others. About 20 hours each. You may also want to start doing some trials or arenas to get certain gear sets; this will require joining guilds or asking in Craglorn zone chats (and Discord or other voice chat system).

I strongly recommend doing the DLCs in the order of Thieves Guild, Dark Brotherhood, Imperial City, then Orsinum (wrothgar), Morrowind (Vvardenfell), Clockwork City, Summerset, Murkmire, (Northern) Elsweyr, Dragonhold (Southern Elsweyr), and then Greymoor (Western Skyrim). Assume 20 hours each for the smaller zones, and more like 30+ for the Expansion zones.

I hope you have a year or so free?

It will take looooooong. Assuming you're doing all the side quests, delves, and public dungeons too, and reading all the dialogue, not just pressing skip and breezing through the main story?

Expect 1-2 afternoons of gametime for every base game zone and smaller DLCs, and at least a full weekend or longer for Chapters. You'll have to get through the following in order:

• EP start: Bleakrock and Bal Foyen, then Stonefalls, Deshaan, Shadowfen, Eastmarch, and The Rift
  - Mages Guild and Fighters Guild questlines along the way
  - Main Quest along the way (from Wailing Prison to Coldharbour)
• Cadwell's Silver and Gold (going through AD and DC zones, to see what they were doing while you did EP - this is highly recommended as you'll meet AD and DC characters in future DLCs and you won't know who they are otherwise).
• Craglorn Lower and Upper questlines
• Imperial City questline (smaller DLC)
• Orsinium (large DLC)
• Thieves Guild (smaller DLC, but the skill line will take time)
• Dark Brotherhood (smaller DLC, but the skill line will take time)
• Morrowind Prologue quest ---> then Morrowind (large DLC - exChapter)
• Clockwork City Prologue quest --> then Clockwork City (smaller DLC)
• Summerset Prologue quest ---> then Summersez (large DLC - exChapter, plus the skill line will take time)
• Murkmire Prologue quest ---> then Murkmire (smaller DLC)
• Wrathstone Dungeon DLC (you can do them on normal, but the story ties into the Season of the Dragon)
• Elsweyr Prologue quest ---> then Elsweyr (large DLC - exChapter)
• Dragonhold Prologue quest ---> then Dragonhold (smaller DLC, but the daily sanctum upgrades will take time)
• Do the Kalgrontiid finale you unlocked by doing Elsweyr and Dragonhold
• Harrowstorm Dungeon DLC (you can do them on normal, but the story ties into the Dark Heart of Skyrim)
• Greymoor Prologue quest ---> then Greymoor (large DLC, it's the current Chapter)

So... it's a LOT. Don't forget that starting with Morrowind, they introduced Prologue quests that give a little hint towards the upcoming DLC and it also lays some groundwork story-wise, so it's worth doing them. And since Elsweyr's year, they tied the Dungeon DLCs into the story too, so you might want to do them on normal to get a full background. (Wrathstone is definitely relevant to the story, and so is Harrowstorm, but Scalebreaker isn't really needed).