且つ

Its Heian Kyoto accent pattern <LF> implies this is same as 終止形 (conclusive form) of verb 勝(か)つ (katsu, “to win”, having low tone <L->). Note existence of かつ (katsu, “(classical) to be bearable”), homophone of that's classical potential form, that might have a sense of "capable of opposing". See also 片(かた) (kata, “one of a pair”).

且(か)つ • (katsu) 

1. and

   簡単(かんたん)に且(か)つ効果的(こうかてき)にできるから。

   Kantan ni katsu kōkateki ni dekiru kara.

   Because it can be done simply and effectively.

• 尚且(なおか)つ (naokatsu)