Plan Zero is listed in the in-game Codex under the  Lore entries for the Sith Warrior.  It is obtained upon completion of the dialogue with Darth Baras following the killing of General Karastace Gonn, the key task of the Set the Table mission.

Code Entry

"Canny observers speculate that Darth Baras has not been wielding his full strength in the power games of the Sith for years. The reason is Plan Zero, an elegant strategy with one purpose: decapitating the Republic’s military leadership in preparation for total war. Darth Baras cares nothing for the Republic military’s obvious heroes. The men who truly matter are behind the scenes. Beginning with the capture of Republic SIS agents in the Outer Rim and culminating in the circumspect cultivation of greedy Senators through proxies, Darth Baras has spent vast resources patiently piecing together information on the Republic’s greatest–and most elusive–generals. Although Plan Zero was composed at Darth Vengean’s directive, it was Baras who has spent almost a decade readying it in secret. No other Sith may interfere, and no Republic spy can warn the Plan Zero targets. Now that the plan has been enacted, Baras’s apprentice will topple one great Republic leader after the next–until war is certain, and total victory is inevitable."
―In-Game Codex((Lore)[src]
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