Base training zone help?

I’m going to do my first sprint tri next year and need a lot of base training. I figure I will do at least 6-9 months of training. So I don’t want do train in vain and really need a zone so here is the long story.

Max heart rate I ever saw 5 years ago was 175. That was twice. Once on top of a hard hill on a long ride when I was really pushing it and once jumping rope after about 45 minutes. So my max then was either 175 or 175x105%= 183 depending on which rate you chose. So five years later it would be either 170 or 178.

As mentioned before a LT finger test gave me 148 for a LT. After a 45 minute ride a coach rated my LT at 152 and if you figure my 45 minute ride as a test my LT would be about 157 which is what I averaged for the ride.

So now what should I use for a base zone?

124-133 which is 70-75 % of 178, max rate

119-127 which is 70-75 % of 170, max rate

125-133 which is 80-85 % of a LT of 157

121-129 which is 80-85 % of a LT of 152

118-125 which is 80-85 % of a LT of 148

So as you can see 118-133 is quite a spread. Any expert comments would be appreciated.

And one more question. This zone would be for riding. How much more of a rate should I train in for my runs?