Since variants don't exist for ZT1, and the ST pack is for ZT2 I assume it is ZT2.
The problem is that they overwright each other. You have three options:
1. Ask the creator of the blue one to change the number at the end to something like _3 or _4.
2. You could do that yourself just for your file.
3. You could open the Snow Tiger pack .z2f file, go to entities/units/animals and delete the TigerBengal folder. That will completely remove the Snow Tiger variant from the bengal.
Hope this helps!