diff --git a/BUILDING b/BUILDING
index 7b3dc9c88..9e9a268be 100644
--- a/BUILDING
+++ b/BUILDING
@@ -149,7 +149,8 @@ information on the supported options.
 The generated makefile mostly just ensures that a `zuo` executable is
 built in a `bin` directory, and then it defers the actual build work
 to `zuo`, which uses the "main.zuo" file. If you have `zuo` installed,
-you can use `zuo` directly instead of `make`. In general, instead of
+you can use `zuo` directly instead of `make`: in that case, you may
+wish to use `./configure ZUO=<zuo>`. In general, instead of
 the command `make X` to build target `X` as described below, you can
 use `zuo . X` (or `bin/zuo . X` after `bin/zuo` is built).
 
@@ -333,7 +334,7 @@ The makefile supports several targets:
  * `make clean`
 
    Removes all built elements from the workarea, and then removes
-   `bin/zuo`.
+   `bin/zuo` (unless configured with `ZUO=<zuo>`).
 
 
 WINDOWS VIA COMMAND PROMPT
diff --git a/build.zuo b/build.zuo
index c21d2caa9..c5896396f 100644
--- a/build.zuo
+++ b/build.zuo
@@ -224,10 +224,15 @@
            token))
 
   (define stexlib
-    (let ((found (assoc "STEXLIB" (hash-ref (runtime-env) 'env))))
-      (if found
-          (cdr found)
-          (at-source "stex"))))
+    (let ([configured (hash-ref config 'STEXLIB "")]
+          [env (assoc "STEXLIB" (hash-ref (runtime-env) 'env))])
+      (cond
+        [(not (equal? "" configured))
+         configured]
+        [env
+         (cdr env)]
+        [else
+         (at-source "stex")])))
   (define stex-sources
     (source-tree stexlib))
 
diff --git a/configure b/configure
index 2b4b594ed..782dd09b7 100755
--- a/configure
+++ b/configure
@@ -93,6 +93,7 @@ default_warning_flags="-Wpointer-arith -Wall -Wextra -Wno-implicit-fallthrough"
 CFLAGS_ADD=
 zlibLib=
 LZ4Lib=
+STEXLIB=
 Kernel=KernelLib
 buildKernelOnly=no
 enableFrompb=yes
@@ -103,6 +104,7 @@ moreBootFiles=
 preloadBootFiles=
 alwaysUseBootFile=
 skipSubmoduleUpdate=
+zuoExternal=
 
 CONFIG_UNAME=`uname`
 
@@ -446,6 +448,12 @@ while [ $# != 0 ] ; do
     LZ4=*)
       LZ4Lib=`echo $1 | sed -e 's/^LZ4=//'`
       ;;
+    STEXLIB=*)
+      STEXLIB=`echo $1 | sed -e 's/^STEXLIB=//'`
+      ;;
+    ZUO=*)
+      zuoExternal=`echo $1 | sed -e 's/^ZUO=//'`
+      ;;
     *)
       echo "option '$1' unrecognized or missing an argument; try $0 --help"
       exit 1
@@ -672,6 +680,8 @@ if [ "$help" = "yes" ]; then
   echo "  STRIP=<strip>                     executable stripper"
   echo "  ZLIB=<lib>                        link to <lib> instead of own zlib"
   echo "  LZ4=<lib>                         link to <lib> instead of own LZ4"
+  echo "  STEXLIB=<stex>                    build docs with <stex> instead of own stex"
+  echo "  ZUO=<zuo>                         build with <zuo> instead of own Zuo"
   echo ""
   echo "Available machine types: $machs"
   echo ""
@@ -889,28 +899,39 @@ submod_instructions () {
     exit 1
 }
 
-if [ ! -f "$srcdir"/zuo/configure ] ; then
-    submod_instructions 'Source in "zuo" is missing'
+if [ "${zuoExternal}" = "" ] ; then
+    if [ ! -f "$srcdir"/zuo/configure ] ; then
+        submod_instructions 'Source in "zuo" is missing'
+    fi
+    ZUO="bin/zuo"
+    RM_ZUO="rm -f bin/zuo"
+    ZUO_TARGET="bin/zuo"
+else
+    ZUO="${zuoExternal}"
+    RM_ZUO="@echo 'Not cleaning external ${zuoExternal}'"
+    ZUO_TARGET="DoNotBuildZuo"
 fi
 
 if [ ! -f "$srcdir"/nanopass/nanopass.ss ] ; then
     submod_instructions 'Source in "nanopass" is missing'
 fi
 
-if [ "${zlibDep}" != "" ] ; then
+if [ "${zlibLib}" = "" ] ; then
     if [ ! -f "$srcdir"/zlib/configure ] ; then
         submod_instructions 'Source in "zlib" is missing'
     fi
 fi
 
-if [ "${LZ4Dep}" != "" ] ; then
+if [ "${LZ4Lib}" = "" ] ; then
     if [ ! -f "$srcdir"/lz4/lib/Makefile ] ; then
         submod_instructions 'Source in "lz4" is missing'
     fi
 fi
 
-if [ ! -f "$srcdir"/stex/Mf-stex ] ; then
-    submod_instructions 'Source in "stex" is missing'
+if [ "${STEXLIB}" = "" ] ; then
+    if [ ! -f "$srcdir"/stex/Mf-stex ] ; then
+        submod_instructions 'Source in "stex" is missing'
+    fi
 fi
 
 # more compile and link flags for c/Mf-unix and mats/Mf-unix
@@ -1083,7 +1104,7 @@ cp "$srcdir"/makefiles/buildmain.zuo main.zuo
 # Some idea, but in the workarea, so it refers to "workarea.zuo" here:
 cp "$srcdir"/makefiles/workmain.zuo $w/main.zuo
 
-# The content of "$w/Makefile" records configuration decisions,
+# The content of "$w/Mf-config" records configuration decisions,
 # and the Zuo build script takes it from there
 cat > $w/Mf-config << END
 srcdir=$srcdir
@@ -1119,6 +1140,7 @@ cursesLib=$cursesLib
 ncursesLib=$ncursesLib
 zlibLib=$zlibLib
 LZ4Lib=$LZ4Lib
+STEXLIB=$STEXLIB
 warningFlags=$warningFlags
 Kernel=$Kernel
 installscriptname=$installscriptname
@@ -1130,6 +1152,10 @@ preloadBootFiles=$preloadBootFiles
 alwaysUseBootFile=$alwaysUseBootFile
 relativeBootFiles=$relativeBootFiles
 
+ZUO=$ZUO
+RM_ZUO=$RM_ZUO
+ZUO_TARGET=$ZUO_TARGET
+
 InstallBin=$installbin
 InstallLib=$installlib
 InstallMan=$installman/man1
diff --git a/makefiles/Makefile.in b/makefiles/Makefile.in
index 3b95f0656..0e3d307d3 100644
--- a/makefiles/Makefile.in
+++ b/makefiles/Makefile.in
@@ -3,8 +3,6 @@ workarea=$(w)
 
 include $(workarea)/Mf-config
 
-ZUO=bin/zuo
-
 .PHONY: build
 build: $(ZUO)
 	+ $(ZUO) $(workarea) MAKE="$(MAKE)"
@@ -144,9 +142,9 @@ pkg: $(ZUO)
 .PHONY: clean
 clean: $(ZUO)
 	+ $(ZUO) $(workarea) clean MAKE="$(MAKE)"
-	rm -f bin/zuo
+	$(RM_ZUO)
 
 # Using `+` here means that $(ZUO) gets built even if `-n`/`--dry-run` is provided to `make`
-$(ZUO): $(srcdir)/zuo/zuo.c
+$(ZUO_TARGET): $(srcdir)/zuo/zuo.c
 	+ mkdir -p bin
 	+ $(CC_FOR_BUILD) -DZUO_LIB_PATH='"'"../zuo/lib"'"' -o $(ZUO) $(srcdir)/zuo/zuo.c