Both Skinks and Kroxigor are separate units and follow all the normal rules. In addition, Kroxigor may see and charge through Skink units (including Chameleon Skinks) that are not fleeing. A Skink unit that has a unit of Kroxigors charge through them must take a leadership test. If this is failed, they may not voluntarily move that turn.
Enemy units charged by Kroxigor through a Skirmish screen may stand and shoot as normal. For the purposes of working out range and whether the unit can stand & shoot at all, measure the distance to the point from which the Kroxigor emerge (ie the front of the Skink unit).
Building an army? Create, validate and share your list with New Recruit, army builder for Warhammer Fantasy Battles (6th definitive edition) and many more games.
Try the builder