Assembly: do MOV or DEC influence zero flag?

In a disassembled code:

movsx eax,[address1]
# a few fpu computations
dec eax
# so many fpu computations
jz label2

If fpu computations do not influence zero flag, then we can assume that it is equal to:

# a few fpu computations
# so many fpu computations
movsx eax,[address1]
dec eax
jz label2

Then, my question is that do mov or dec have any influence on zero flag?

Of course you should look this up in the manuals but here's a general rule:

• Instructions that move stuff around don't modify the flags.
• Instructions that do computations will modify the flags.

So movsx falls in the first category and will not change any flag.
But dec clearly does a computation and most certainly changes several flags including the ZeroFlag.