It free and it does a reasonable job. You just have to make sure you align before stacking. Got some very good results. Obviously needs a little patience. There are paid for alternatives but for free you can't go wrong. Installed on Windows 10 64-bit. Excellent program.
CombineZP is super.
I'm working with fungi, the documentation of spores with 1000x magnification
and other microscope-fotos (some macros, also) need your program!
I can no longer do without CombineZP.