DCMTK undefined reference

compiling pFire with  default DCMTK configuration:
`
/opt/rh/devtoolset-9/root/usr/libexec/gcc/x86_64-redhat-linux/9/ld: /home/tartarini/local/libs/DCMTK/3.6.5/lib64/libdcmdata.a(dcistrmz.cc.o): undefined reference to symbol 'inflateInit2_'
/opt/rh/devtoolset-9/root/usr/libexec/gcc/x86_64-redhat-linux/9/ld: /lib64/libz.so.1: error adding symbols: DSO missing from command line
`