That comparison is laughable, and completely disrespectful to marc gasol. Marc gasol is the best defensive center in the league, while Zeller is softer than tissues and ducks out of the way when opponents attack the basket.
Zeller is an offensive center that will disappear at times on the court. He will also often get out rebounded and pushed around. That is more Mark Blount than a defensive first, high low post capable, large, scrappy, load of a player that Marc Gasol is.
I think Marc Gasol is way overrated on these forums, and our own players (e.g. Zeller) typically get way underrated. I'm not trying to say Zeller is on the level of Gasol right now, but comparing the two players based on past production, they are closer than you think.
1 - Rebounding Zeller's rebounding production at the age of 24 and 25 have been dead on par with what Gasol put up at the same age.
At 24 year old Zeller averaged 9.7 rebounds per 36 with a 15.1% rebound percentage and Gasol averaged 8.6 rebounds per 36 with a rebound rate of 14.7%.
At 25 years old Zeller averaged 9.7 rebounds per 36 with a 14.7% rebound percentage, and Gasol averaged 9.3 rebounds per 36 with a 15.1% rebound percentage.
Those were the two best rebounding seasons of Gasol's career, and he has since regressed significantly as a rebounder. To the point where his current career rebound average (8.4 Reb Per-36) and rebound percentage (13.8%) are now on par with the career numbers of Brook Lopez- a man who is regularly mocked for his laughably bad rebounding.
Unless Zeller's rebounding coincidentally shows a similarly significant drop off starting with next season (possible, but unlikely) you'll probably find Zeller will be a better career rebounder than Gasol.
2 - OffenseMarc Gasol is far from an elite / dominant offensive player. He's a skilled and versatile offensive player though, because he scores very well in the paint, has a very nice mid-range jumper, gets to the line very well, is a solid free throw shooter, and is a very good passer for a big. Zeller can make all of those same claims.
At the age of 24 Gasol shot 67% inside 3 feet, 36% from 10-16 feet and 45% from 16 feet to the three point line. He had a free throw rate of 56% and shot 73% from the line. He averaged 2 assists per 36 minute and had an assist percentage of 9.7%.
Zeller at 24 shot 65% inside 3 feet, 52% from 10-16 feet and 47% from 16 feet to the three point line. He had a free throw rate of 42% and shot 72% from the line. He averaged 1.2 assists per 36 and had an assist percentage of 7.4%.
At 25 Gasol shot 70% inside 3 feet, 42% from 10-16 feet and 30% from 16 feet to the three point line. He had a free throw rate of 58% and shot 67% from the line. He averaged 2.4 assists per 36 minutes and had an assist percentage of 10.2%.
Zeller at 25 shot 63% inside 3 feet, 60% from 10-16 feet and 48% from 16 feet to the three point line. He had a free throw rate of 30% and shot 82% from the line. He averaged 2.4 assists per 36 minutes and had an assist percentage of 10.8%.
Now looking at these numbers Gasol obviously shot at a high percentage inside the paint and also got to the line more, but Zeller has clearly had a far superior midrange game. As passers that have been pretty similar up to the age of 25.
It's also worth noting that the free throw rates Gasol put up in those two seasons were the highest of his career - after the age of 25 he never had a FTR above 42.8%, so that part of his game has regressed somewhat (though still very good).
Gasol's TS% was 59% at 24 years old and 62% at the age of 25. Zeller's was 58% at the age of 25 and 60% at the age of 25.
In terms of pure scoring output, Gasol averaged 13.9 Points Per-36 when he was 24 years old and 14.7 Points Per-36 when he was 25. Zeller averaged 13.7 Points Per-36 when he was 24 and 17.3 Points Per-36 when he was 25.
Offensively, Zeller is every bit as good an offensive player now as Gasol was when he was the same age.
3 - DefenseUnfortunately I can't pull up "Real Plus Minus" stats from when Gasol was 24/25 since the statistic was never recorded.
I can say that Marc Gasol was an elite defensive player in 2013/14 however, as his DRPM of +5.23 was good enough to rank him 4th overall in the league and 1st among centers.
However this year his numbers regressed significantly. His DRPM dropped by around 3.5 points down to +1.91 which ranked him 57th over all and 20th among centers. Ranking top 50 in the NBA is nothing to scoff at by any means, but it's a major drop from where he was - it's the difference between 'elite' and merely 'very good'.
Interestingly, Tyler Zeller has had good DRPM numbers in both of his last two seasons. in 2013/14 he had a DRPM of +1.49 which ranked him 93rd overall and 29th among centers. That's basically the top 25% percent of NBA players defensively.
In 2014/15 Zeller was similarly good, with his DRPM of +1.36 ranking him 87th overall and 30th among centers.
Still clearly not as effective as Gasol defensively, but in 2014/15 he wasn't too far behind at all.
One thing we CAN compare from the age of 24/25 is shot blocking.
Gasol averaged 1.3 blocks Per 36 (2.9% block percentage) at the age of 24, and 1.6 blocks per 36 (3.4% block percentage) at the age of 25.
By comparison Zeller averaged 1.3 Blocks Per 36 (3.0% Block Percentage) at the age of 24, and 1.1 Blocks Per 36 Minutes (2.3% Block Percentage) at the age of 25.
Defensively Gasol is obviously the better player right now, but I'd love to see some advanced defensive stats from when Gasol was 24/25 (Def Rating, on/off or something) to compare against Zeller. While Gasol would no doubt have better stats on that end than Zeller, I suspect the difference might not be as big as people think.
I think we should give the OP a break because if you look at these two guys closely, there are certainly a lot of statistical similarities. I don't think the comparison is unreasonable and I certainly don't think it's insulting to Marc Gasol. It wouldn't shock me to see Zeller one day be as good as Gasol overall - though I suspect Zeller's talented would lean a little more towards the offensive end.