Hi tech -- clang says zclose is an unused function. Seems to check out.
~Brian Index: zopen.c =================================================================== RCS file: /cvs/src/usr.bin/compress/zopen.c,v retrieving revision 1.21 diff -u -p -u -p -r1.21 zopen.c --- zopen.c 3 Sep 2016 11:41:10 -0000 1.21 +++ zopen.c 23 May 2017 03:31:05 -0000 @@ -343,12 +343,6 @@ z_close(void *cookie, struct z_info *inf return (rval); } -static int -zclose(void *cookie) -{ - return z_close(cookie, NULL, NULL, NULL); -} - /*- * Output the given code. * Inputs: