Any idea on this error ?

Installation warning --> Zenphoto core files [Some files are missing or their filemtimes seem out of variance]

Perhaps there was a problem with the upload. You should check the following files:
.htaccess
zp-core/locale/sl_SI

An error in RC1's package list. Should be fixed in RC2

So I should just ignore this and continue with the installation?

If everything works as expected you can ignore that (the locale is not necessary to run at all while the htaccess file is if you want to use mod_rewrite urls).