The difference in weight between a ZL1, as equipped, and an LS7'd "Base" 1ZE, as listed, could be 200-250 lb. ZL1 contains 2SS+ trimmings, all the electronic doodads, MRC etc. etc.
ZL1 = 4120
1SS = 3850 (-270)
LS3 = LS7
Enhanced FE4 = very little over FE4, and less than MRC
MG9 + Brembo 6/4 + HD Diff - (2) 6-way Seats - Forged 20s etc. = 3875/3920 end result...3875 or so with enhanced FE4, 3920 with MRC.