Indeed, they are planning a plan, (86:15)

Almuntakhab Fi Tafsir Alquran Alkarim

They - the infidels - in their effort to misguide people and divert them from Allahs path keep plotting and continue to scheme

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(86:15) They are devising a guile, *8

Indeed, they are planning a plan, meaning

*8) That is, these disbelievers are devising every kind of plan to defeat the invitation of the Qur'an; they wish to blow out this candle; they are creating aII sorts of doubts In the people's minds: they are inventing false accusations against the Prophet who has brought it, so as to frustrate his mission in the world and perpetuate the darkness of ignorance and unbelief which hr is struggling so hard to remove.
 

Indeed, they are planning a plan, meaning in Urdu

یہ لوگ چالیں چل رہے ہیں