what? riflmen AI sucks? Bazooka has a much higher fire rate then shreks, lower cost and has splash damage and its very VERY effective vs light and medium vehicles, its only against heavies it will struggle but it will still force axis heavies back because of the fear of being snared
First, no handheld AT weapon is in any way useful against infantry with exception of guards PTRS.
Second, zooks have ~55% to pen P4 at max range as that P4 isn't going to be closer usually, while shrecks have 80+% chance to pen at the same distance, which means zooks will outperform shrecks only if there is MUCH MORE of them.
Spamming zook squads isn't exactly the best way to win either, because this thing called pop cap exists and regardless of how many zooks you have, not having any armor in late game or having upkeep so high to not be able to sustain this army isn't going to win you anything, so cut down on zook fantasy.