The problem is the Z spring is a 8.1 Kg where a LT is a 4.2kg  If you put a z spring on a Lt shock your over sprung unless your 200lb + and ride really aggressive on smaller jumps. Or with a lt spring on the Z shock your under sprung and valved too stiff. Either way you end up sprung and valved wrong. Unless you buy the correct or close spring rate, take it apart, rebuild & revalve a shock. 
In the end a Z shock is @ 1/4 too long and will bind at full extension, It is already a couple mm less travel than a Lt shock. 

The Z shock is a good QUICK fix to get back on the trail, to make it Rite, Stick with a LT Shock and get it redone or buy a new shock correctly set up already.