Common ground
All three exegetes agree that the word 'zann' in this verse means certainty/definite knowledge (yakîn) and not doubt/uncertainty. While Taberî and Kurtubî ground this view directly through linguistic/rhetorical analysis and testimony from Arabic poetry, Beydâvî also accepts the same meaning (firmly believing that one will meet Allah or be called to account). Furthermore, all three present this interpretation as the reason why those possessed of khushû' do not find prayer burdensome/bear it with patience, and they commonly employ the method of linguistic substantiation as common ground.
Differences
Taberî addresses the matter primarily as a linguistic issue; he places emphasis on poetry testimonies and exegetical reports (Ibn Jurayj, Mujahid, Suddi) to prove that 'zann' is among words with opposite meanings (ezdad), using transmission (riwayal) and reasoning (dirayal) in a balanced manner. Kurtubî, on the other hand, takes the view of the majority (cumhur) as the basis and brings the matter to a debated ground; he mentions an alternative interpretation (in the sense of doubt, with the supply of words 'with their sins'), and criticizes this through Ibn Atiyya's mouth as 'contrived', thus reflecting a conflict of views within itself. Beydâvî, however, presents a much more concise linguistic-rhetorical approach, and also adds an additional dimension of transmission by including the difference in Ibn Mas'ud's reading and hadith reports, thereby moving to a somewhat different variety of sources than Taberî and Kurtubî. These differences may stem from Taberî's early period exegesis method using more extensive transmission material, Kurtubî's juristic-polemical inclination, and Beydâvî's summarizing/rhetorical exegesis style.
Historical context
Taberî (early period, pioneer of transmission-based exegesis) grounds the matter with extensive transmission material, while Kurtubî who came after him solidified this linguistic finding as 'the view of the majority' and strengthened it by eliminating debated alternative views. Beydâvî, in a later period, arrived at the same conclusion by summarizing the accumulated material from previous exegeses and employing a reasoning-weighted style, but also included an additional element such as the difference in reading (qirâ'a). That is, over three periods, the interpretation 'zann=certainty' remained the fixed main line, but the method of reaching this conclusion and the supporting evidence used (from transmission weight toward concise reasoning) differed over time.