Redirects with two wp installations

On my hosting platform I have two WP installations. One for the main domain (splendesco.nl) and one for a subdomain (zakelijk.splendesco.nl) in a subfolder. I had redirects set up in de root htaccess as follows
Redirect 301 /workshops /workshops-en-trainingen/

That was all working fine. After creating the subdomain however, the subdomain would also pick up the redirects, so I changed the code.

The complete htaccess in the root folder is now (I have numbered the redirect lines)

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
# custom redirects
Options +FollowSymLinks -MultiViews
#
RewriteCond %{HTTP_HOST} !^www\.splendesco\.nl$ [NC]
RewriteRule .? –[S=5]
1. > RewriteRule ^/workshop\-enneagram/(.*)$ /workshops\-en\-trainingen/workshop\-enneagram/$1 [R=301,NC,L]
2. > RewriteRule ^/workshop/(.*)$ /workshops\-en\-trainingen/$1 [R=301,NC,L]
3. > RewriteRule ^/workshops/(.*)$ /workshops\-en\-trainingen/$1 [R=301,NC,L]
4. > RewriteRule ^/training/(.*)$ /workshops\-en\-trainingen/$1 [R=301,NC,L]
5. > RewriteRule ^/trainingen/(.*)$ /workshops\-en\-trainingen/$1 [R=301,NC,L]
# end of custom redirects
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

This only partially works. Lines 1 and 3 work as expected. Lines 4 and 5 keep giving me a 404 and do not redirect. Line 2 does an incoreect redirect to https://www.splendesco.nl/workshops-en-trainingen/workshop-enneagram/.

I already tried the SEO redirect plugin. The redirects then works, but also the problem is back with them also being called from the subdomain.

So basically the questions is: if the above htaccess has problems, where are the problems, or: how would I set up redirects in such a way that they all work ONLY on the main domain and not on the subdomain.

Sorry for the long post. Thanks for your help.

John