Next week I'm going to us and I will buy a new phone. I was thinking of buying a Moto Z Force. But I heard it is only available for Verizon. I'm from Brazil and would like to know if even if the version from the Motorola site is locked for Verizon and if I would have any problems in using this phone here in Brazil.
Brazilian carriers appear to use 3, 7, 28, and 38. As such, you should by default expect US Verizon phones not to work with LTE in Brazil since there are no overlapping bands.
However, the Verizon Z Force supports bands 2-5, 7, and 13. So it's quite possible that it would work on some Brazilian carriers using bands 3 and 7.
(The same basic process of finding overlap applies for 3G bands, GSM voice, etc. if you don't care about LTE specifically.)
You should contact Motorola directly to find out whether the version they sell is locked, and (if so) whether it can be easily unlocked.
Yes , US VZ Telephony has a different 4G protocol . You will not be able to use 4G in Brazil.