Swapping hands cancels zoom

code/game/objects/items.dm

@@ -680,6 +680,10 @@ modules/mob/living/carbon/human/life.dm if you die, you will be zoomed out.
 /obj/item/proc/is_hot()
 	return FALSE
 
+// Called when you swap hands away from the item
+/obj/item/proc/in_inactive_hand(mob/user)
+	return
+
 // My best guess as to why this is here would be that it does so little. Still, keep it under all the procs, for sanity's sake.
 /obj/item/device
 	icon = 'icons/obj/device.dmi'

code/modules/mob/living/carbon/human/inventory.dm

@@ -340,6 +340,11 @@ This saves us from having to call add_fingerprint() any time something is put in
 	if(W.action_button_name)
 		update_action_buttons()
 
+	if(W.zoom)
+		W.zoom()
+
+	W.in_inactive_hand(src)
+
 	return 1
 
 //Checks if a given slot can be accessed at this time, either to equip or unequip I

code/modules/mob/living/living.dm

@@ -1113,6 +1113,13 @@ default behaviour is:
 		else
 			hud_used.l_hand_hud_object.icon_state = "l_hand_inactive"
 			hud_used.r_hand_hud_object.icon_state = "r_hand_active"
+
+	// We just swapped hands, so the thing in our inactive hand will notice it's not the focus
+	var/obj/item/I = get_inactive_hand()
+	if(I)
+		if(I.zoom)
+			I.zoom()
+		I.in_inactive_hand(src)	//This'll do specific things, determined by the item
 	return
 
 /mob/living/proc/activate_hand(var/selhand) //0 or "r" or "right" for right hand; 1 or "l" or "left" for left hand.