1) Rename 'admin' folder to 'zcadmin' and zip it because 'admin' folder is not allowed.

2) zc_install/includes/classes/installer.php

3) Please replace /admin to /zcadmin so that we can Upgrade properly in the following files in the zencart.zip:
zc_install/includes/classes/installer.php
zc_install/includes/modules/pages/inspect/header_php.php
zc_install/includes/templates/template_default/templates/finished_default.php

(Not required since 1.5.5)

4) Make `reset_token` column blank in `prezc_admin` table for admin entry. If this is not blank then it will ask for password change after first login. Also configure `pwd_last_change_date` as [[regtime]] in same table, if not configured and kept default '1970-01-01 00:00:00', still it will ask to change password.

5) Install without demo data

6) Third link has been disabled for every security releases of 1.5.5 for upgrades : changes made in upgrade.php : 1.5.5 to 1.5.5f, 1.5.5a to 1.5.5f, 1.5.5b to 1.5.5f, 1.5.5c to 1.5.5f, 1.5.5d to 1.5.5f, 1.5.5e to 1.5.5f.

Since 1.5.5a, 1.5.5b, 1.5.5c, 1.5.5d, 1.5.5e , 1.5.5f are just patches and have no database changes to be done. However the files needs to be replaced. Check in next version.
(We have disabled from 2.2.1 to 2.2.2 as well, as it didn't show upgrade option(only clean install option) and shows 'your database seems to be current')

7) Keep "Session Directory" [[softpath]]/cache in `configuration` table.

8) PHP REQUIREMENT LINK: https://docs.zen-cart.com/user/first_steps/server_requirements/

9)We keep 'GLOBAL_AUTH_KEY' blank under `{{dbprefix}}configuration` table, since it is created post we swget the admin url in install.php.
10) If you get 'Problems with session support' error in red while starting manual install enable output buffering in php.ini i.e change output_buffering = Off to output_buffering = On
(Not needed in 2.2.2, as they have fixed the space in zc_install/includes/version.php space in <?php tag, which was causing this), mentioned here https://github.com/zencart/zencart/pull/7566)